35339

LT1206 250mA/60MHz Current Feedback Amplifier FeaTures n n n n n n n n n n n DescripTion The LT®1206 is a current feedback amplifier with high output current drive capability and excellent video characteristics. The LT1206 is stable with large capacitive loads, and can easily supply the large currents required by the capacitive loading. A shutdown feature switches the device into a high impedance, low current mode, reducing dissipation when the device is not in use. For lower bandwidth applications, the supply current can be reduced with a single external resistor. The low differential gain and phase, wide bandwidth, and the 250mA minimum output current drive make the LT1206 well suited to drive multiple cables in video systems. The LT1206 is manufactured on Linear Technology’s proprietary complementary bipolar process. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 250mA Minimum Output Drive Current 60MHz Bandwidth, AV = 2, RL = 100Ω 900V/µs Slew Rate, AV = 2, RL = 50Ω 0.02% Differential Gain, AV = 2, RL = 30Ω 0.17° Differential Phase, AV = 2, RL = 30Ω High Input Impedance, 10MΩ Wide Supply Range, ±5V to ±15V Shutdown Mode: IS < 200µA Adjustable Supply Current Stable with CL = 10,000p Available in 8-Pin DIP and SO and 7-Pin DD and TO-220 Packages applicaTions n n n n n Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers Buffers Typical applicaTion Noninverting Amplifier with Shutdown 15V VIN Large-Signal Response, CL = 10,000pF + LT1206 COMP CCOMP – S/D** 0.01µF* –15V RF 15V 5V 24k 74C906 1206 TA01 VOUT RG ENABLE *OPTIONAL, USE WITH CAPACITIVE LOADS **GROUND SHUTDOWN PIN FOR NORMAL OPERATION VS = ±15V RL = RG = 3k RL = ∞ 500ns/DIV 1206 TA01b 1206fb 1 LT1206 absoluTe MaxiMuM raTings (Note 1) Supply Voltage ........................................................ ±18V Input Current........................................................ ±15mA Output Short-Circuit Duration (Note 2) ......... Continuous Specified Temperature Range (Note 3) ........ 0°C to 70°C Operating Temperature Range .................–40°C to 85°C Junction Temperature ........................................... 150°C Storage Temperature Range .................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................... 300°C pin conFiguraTion TOP VIEW NC 1 –IN 2 +IN 3 S/D* 4 8 7 6 5 V + TOP VIEW V + 1 8 7 6 5 V+ OUT V– COMP OUT V– COMP –IN 2 +IN 3 S/D* 4 N8 PACKAGE 8-LEAD PLASTIC DIP θJA = 100°C/W FRONT VIEW 7 6 5 4 3 2 1 OUT V– COMP V+ S/D* +IN –IN S8 PACKAGE 8-LEAD PLASTIC SO θJA = 60°C/W FRONT VIEW 7 6 5 4 3 2 1 T7 PACKAGE 7-LEAD PLASTIC TO-220 θJA = 5°C/W OUT V– COMP V+ S/D* +IN –IN TAB IS V+ TAB IS V+ R PACKAGE 7-LEAD PLASTIC DD θJA = 30°C/W orDer inForMaTion LEAD FREE FINISH LTC1206CN8#PBF LT1206CS8#PBF LT1206CR#PBF LT1206CT7#PBF LEAD BASED FINISH LTC1206CN8† LT1206CS8** LT1206CR† LT1206CT7† TAPE AND REEL LTC1206CN8#TRPBF LT1206CS8#TRPBF LT1206CR#TRPBF LT1206CT7#TRPBF TAPE AND REEL LTC1206CN8#TR LT1206CS8#TR LT1206CR#TR LT1206CT7#TR PART MARKING* LT1206 1206 LT1206 LT1206 PART MARKING* LT1206 1206 LT1206 LT1206 PACKAGE DESCRIPTION 8-Lead Plastic DIP 8-Lead Plastic SO 7-Lead Plastic DD 7-Lead Plastic TO-220 PACKAGE DESCRIPTION 8-Lead Plastic DIP 8-Lead Plastic SO 7-Lead Plastic DD 7-Lead Plastic TO-220 TEMPERATURE RANGE –40°C to 85°C –40°C to 85°C –40°C to 85°C –40°C to 85°C TEMPERATURE RANGE –40°C to 85°C –40°C to 85°C –40°C to 85°C –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. **Ground shutdown pin for normal operation. †See Note 3. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 1206fb 2 LT1206 elecTrical characTerisTics SYMBOL PARAMETER Input Offset Voltage VOS IIN+ IIN– en +in –in RIN CIN CMRR Input Offset Voltage Drift Noninverting Input Current Inverting Input Current l The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ 15V, pulse tested, VS/D = 0V, unless otherwise noted. CONDITIONS l l l MIN Input Noise Voltage Density Input Noise Current Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range Common Mode Rejection Ratio PSRR AV ROL VOUT Inverting Input Current Common Mode Rejection Power Supply Rejection Ratio Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection VS = ±5V to ±15V Large-Signal Voltage Gain VS = ±15V, VOUT = ±10V, RL = 50Ω VS = ±5V, VOUT = ±2V, RL = 25Ω Transresistance, ΔVOUT /ΔIIN– VS = ±15V, VOUT = ±10V, RL = 50Ω VS = ±5V, VOUT = ±2V, RL = 25Ω Maximum Output Voltage Swing VS = ±15V, RL = 50Ω VS = ±15V, RL = 25Ω f = 10kHz, RF = 1k, RG = 10Ω, RS = 0Ω f = 10kHz, RF = 1k, RG = 10Ω, RS = 10k f = 10kHz, RF = 1k, RG = 10Ω, RS = 10k VIN = ±12V, VS = ±15V VIN = ±2V, VS = ±5V VS = ±15V VS = ±15V VS = ±5V VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±2V VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±2V VS = ±5V to ±15V VS = ±5V to ±15V l l l l l l l l l l l l l l l l l 1.5 0.5 ±12 ±2 55 50 60 UNITS mV mV 10 µV/°C ±2 ±8 µA ±25 µA ±10 ±60 µA ±100 µA 3.6 nV/√Hz 2 pA/√Hz 30 pA/√Hz 10 MΩ 5 MΩ 2 pF ±13.5 V ±3.5 V 62 dB 60 dB 0.1 10 µA/V 0.1 10 µA/V 77 dB 30 500 nA/V 0.7 71 68 260 200 ±12.5 ±3.0 500 20 12 1200 30 35 17 200 10 5 µA/V dB dB kΩ kΩ V V V V mA mA mA mA µA µA V/µs % Deg MHz MHz MHz MHz TYP ±3 MAX ±10 ±15 IOUT IS Maximum Output Current Supply Current Supply Current, RS/D = 51k (Note 4) Positive Supply Current, Shutdown Output Leakage Current, Shutdown Slew Rate (Note 5) Differential Gain (Note 6) Differential Phase (Note 6) Small-Signal Bandwidth RL = 1Ω VS = ±15V, VS/D = 0V VS = ±15V VS = ±15V, VS/D = 15V VS = ±15V, VS/D = 15V AV = 2 VS = ±15V, RF = 560Ω, RG = 560Ω, RL = 30Ω VS = ±15V, RF = 560Ω, RG = 560Ω, RL = 30Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 620Ω, RL = 100Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 649Ω, RL = 50Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 698Ω, RL = 30Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 825Ω, RL = 10Ω l l l l 55 55 100 75 ±11.5 ±10.0 ±2.5 ±2.0 250 SR 400 BW 900 0.02 0.17 60 52 43 27 Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: Applies to short circuits to ground only. A short circuit between the output and either supply may permanently damage the part when operated on supplies greater than ±10V. Note 3: Commercial grade parts are designed to operate over the temperature range of –40°C to 85°C but are neither tested nor guaranteed beyond 0°C to 70°C. Industrial grade parts tested over –40°C to 85°C are available on special request. Consult factory. Note 4: RS/D is connected between the shutdown pin and ground. Note 5: Slew rate is measured at ±5V on a ±10V output signal while operating on ±15V supplies with RF = 1.5k, RG = 1.5k and RL = 400Ω. Note 6: NTSC composite video with an output level of 2V. 1206fb 3 LT1206 sMall-signal banDwiDTh IS = 20mA Typical, Peaking ≤ 0.1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 562 649 732 619 715 806 576 649 750 442 511 649 RG 562 649 732 – – – 576 649 750 48.7 56.2 71.5 –3dB BW (MHz) 48 34 22 54 36 22.4 48 35 22.4 40 31 20 –0.1dB BW (MHz) 21.4 17 12.5 22.3 17.5 11.5 20.7 18.1 11.7 19.2 16.5 10.2 AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 681 768 887 768 909 1k 665 787 931 487 590 768 RG 681 768 887 – – – 665 787 931 536 64.9 84.5 –3dB BW (MHz) 50 35 24 66 37 23 55 36 22.5 44 33 20.7 –0.1dB BW (MHz) 19.2 17 12.3 22.4 17.5 12 23 18.5 11.8 20.7 17.5 10.8 VS = ±5V, RS/D = 0Ω VS = ±15V, RS/D = 0Ω 1 1 2 2 10 10 IS = 10mA Typical, Peaking ≤ 0.1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 576 681 750 665 768 845 590 681 768 301 392 499 RG 576 681 750 – – – 590 681 768 33.2 43.2 54.9 –3dB BW (MHz) 35 25 16.4 37 25 16.5 35 25 16.2 31 23 15 –0.1dB BW (MHz) 17 12.5 8.7 17.5 12.6 8.2 16.8 13.4 8.1 15.6 11.9 7.8 AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 634 768 866 768 909 1k 649 787 931 301 402 590 RG 634 768 866 – – – 649 787 931 33.2 44.2 64.9 –3dB BW (MHz) 41 26.5 17 44 28 16.8 40 27 16.5 33 25 15.3 –0.1dB BW (MHz) 19.1 14 9.4 18.8 14.4 8.3 18.5 14.1 8.1 15.6 13.3 7.4 VS = ±5V, RS/D = 10.2k VS = ±15V, RS/D = 60.4k 1 1 2 2 10 10 IS = 5mA Typical, Peaking ≤ 0.1dB AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 604 715 681 768 866 825 634 750 732 100 100 100 RG 604 715 681 – – – 634 750 732 11.1 11.1 11.1 –3dB BW (MHz) 21 14.6 10.5 20 14.1 9.8 20 14.1 9.6 16.2 13.4 9.5 –0.1dB BW (MHz) 10.5 7.4 6.0 9.6 6.7 5.1 9.6 7.2 5.1 5.8 7.0 4.7 AV –1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 619 787 825 845 1k 1k 681 845 866 100 100 100 RG 619 787 825 – – – 681 845 866 11.1 11.1 11.1 –3dB BW (MHz) 25 15.8 10.5 23 15.3 10 23 15 10 15.9 13.6 9.6 –0.1dB BW (MHz) 12.5 8.5 5.4 10.6 7.6 5.2 10.2 7.7 5.4 4.5 6 4.5 1206fb VS = ±5V, RS/D = 22.1k VS = ±15V, RS/D = 121k 1 1 2 2 10 10 4 LT1206 Typical perForMance characTerisTics Bandwidth vs Supply Voltage 100 90 – 3dB BANDWIDTH (MHz) 80 70 60 50 40 30 20 10 0 4 6 RF = 1k RF = 1.5k 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 0 4 6 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 100 RF = 750 RF = 470 RF = 560 RF = 680 PEAKING ≤ 0.5dB PEAKING ≤ 5dB AV = 2 RL = 100 –3dB BANDWIDTH (MHz) 50 Bandwidth vs Supply Voltage PEAKING ≤ 0.5dB PEAKING ≤ 5dB RF = 560 RF = 750 RF = 1k RF = 2k 10 AV = 2 RL = 10 FEEDBACK RESISTOR ( ) 10k Bandwidth and Feedback Resistance vs Capacitive Load for 0.5dB Peak 100 BANDWIDTH –3dB BANDWIDTH (MHz) 40 30 1k FEEDBACK RESISTOR AV = 2 RL = ∞ VS = 15V CCOMP = 0.01µF 1 10 100 1000 CAPACITIVE LOAD (pF) 10 20 1 10000 1206 G03 1206 G01 1206 G02 Bandwidth vs Supply Voltage 100 90 –3dB BANDWIDTH (MHz) 80 70 60 50 40 30 20 10 0 4 6 RF = 470 RF = 680 RF = 1.5k 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 0 RF =390 RF = 330 PEAKING ≤ 0.5dB PEAKING ≤ 5dB AV = 10 RL = 100 – 3dB BANDWIDTH (MHz) 50 Bandwidth vs Supply Voltage PEAKING ≤ 0.5dB PEAKING ≤ 5dB AV = 10 RL = 10 FEEDBACK RESISTOR ( ) 10k Bandwidth and Feedback Resistance vs Capacitive Load for 5dB Peak 100 BANDWIDTH –3dB BANDWIDTH (MHz) 40 RF = 560 RF = 680 RF = 1k 10 RF = 1.5k 30 1k 10 20 FEEDBACK RESISTOR 0 100 AV = +2 RL = ∞ VS = 15V CCOMP = 0.01µF 4 6 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 1 10 100 1k CAPACITIVE LOAD (pF) 1 10k 1206 G04 1206 G05 1206 G06 Differential Phase vs Supply Voltage 0.50 R = R = 560 F G AV = 2 N PACKAGE 0.40 0.30 RL = 30 RL = 50 RL = 150 0 5 7 11 13 9 SUPPLY VOLTAGE (±V) 15 1206 G07 Differential Gain vs Supply Voltage 0.10 RL = 15 DIFFERENTIAL GAIN (%) RL = 15 SPOT NOISE (nV/√Hz OR pA/√Hz) RF = RG = 560 AV = 2 N PACKAGE 100 Spot Noise Voltage and Current vs Frequency DIFFERENTIAL PHASE (DEG) 0.08 0.06 –in RL = 30 0.04 0.02 RL = 150 0 5 7 11 13 9 SUPPLY VOLTAGE (±V) 15 1206 G08 10 en in 1 10 0.20 0.10 RL = 50 100 1k 10k FREQUENCY (Hz) 100k 1206 G09 1206fb 5 LT1206 Typical perForMance characTerisTics Supply Current vs Supply Voltage 24 22 SUPPLY CURRENT (mA) 20 18 16 14 12 10 4 TJ = 125°C TJ = 25°C VS/D = 0V 25 TJ = – 40°C 20 SUPPLY CURRENT (mA) RSD = 0 Supply Current vs Ambient Temperature, VS = ±5V AV = 1 RL = ∞ N PACKAGE SUPPLY CURRENT (mA) 25 Supply Current vs Ambient Temperature, VS = ±15V RSD = 0 AV = 1 RL = ∞ N PACKAGE 20 15 RSD = 10.2k 10 RSD = 22.1k 15 RSD = 60.4k RSD = 121k 5 TJ = 85°C 10 5 6 14 12 10 8 SUPPLY VOLTAGE (±V) 16 18 0 –50 –25 50 25 0 75 TEMPERATURE (C) 100 125 0 –50 –25 50 25 0 75 TEMPERATURE (C) 100 125 1206 G10 1206 G11 1206 G12 Supply Current vs Shutdown Pin Current 20 18 16 SUPPLY CURRENT (mA) 14 12 10 8 6 4 2 0 0 100 300 400 200 SHUTDOWN PIN CURRENT (µA) 500 1206 G13 – 0.5 COMMON-MODE RANGE (V) –1.0 –1.5 –2.0 2.0 1.5 1.0 0.5 V– –50 –25 0 25 50 75 TEMPERATURE (C) 100 125 OUTPUT SHORT-CIRCUIT CURRENT (A) VS = ±15V V+ Input Common Mode Limit vs Junction Temperature 1.0 0.9 0.8 Output Short-Circuit Current vs Junction Temperature SOURCING 0.7 0.6 0.5 0.4 0.3 –50 –25 SINKING 0 50 25 75 TEMPERATURE (C) 100 125 1206 G14 1206 G15 V+ OUTPUT SATURATION VOLTAGE (V) –1 –2 –3 –4 4 3 2 1 Output Saturation Voltage vs Junction Temperature VS = ±15V 70 RL = 2k RL = 50Ω POWER SUPPLY REJECTION (dB) 60 50 40 30 20 10 Power Supply Rejection Ratio vs Frequency NEGATIVE POSITIVE RL = 50Ω VS = ±15V RF = RG = 1k SUPPLY CURRENT (mA) 1M 10M FREQUENCY (Hz) 100M 1206 G17 Supply Current vs Large-Signal Output Frequency (No Load) 60 AV = 2 RL = ∞ V = ±15V 50 VS = 20V OUT P-P 40 RL = 50Ω RL = 2k 30 20 10 10k V– –50 –25 0 25 50 75 TEMPERATURE (C) 100 125 0 10k 100k 100k 1M 10M 1206 G18 FREQUENCY (Hz) 1206 G16 1206fb 6 LT1206 Typical perForMance characTerisTics Output Impedance vs Frequency 100 VS = ±15V IO = 0mA RS/D = 121k 100k Output Impedance in Shutdown vs Frequency AV = 1 RF = 1k VS = ±15V DISTORTION (dBc) –30 –40 –50 –60 –70 –80 2nd and 3rd Harmonic Distortion vs Frequency VS = ±15V VO = 2VP-P RL = 10Ω 2nd 3rd 2nd OUTPUT IMPEDANCE (Ω) 1 RS/D = 0Ω OUTPUT IMPEDANCE (Ω) 10 10k 1k 0.1 RL = 30Ω 100 3rd 0.01 100k 1M 10M 100M 1206 G19 10 100k –90 1M 10M 100M 1206 G20 1 FREQUENCY (Hz) FREQUENCY (Hz) 2 45 3 FREQUENCY (MHz) 6 7 8 9 10 1206 G21 3rd Order Intercept vs Frequency 60 VS = ±15V RL = 50Ω RF = 590Ω RG = 64.9Ω Test Circuit for 3rd Order Intercept + LT1206 PO 3rd ORDER INTERCEPT (dBm) 50 – 590Ω 65Ω MEASURE INTERCEPT AT PO 50Ω 1206 TC01 40 30 20 10 0 5 10 15 20 FREQUENCY (MHz) 25 30 1206 G22 1206fb 7 LT1206 siMpliFieD scheMaTic V+ TO ALL CURRENT SOURCES Q2 Q18 Q17 1.25k +IN Q1 V– –IN CC Q6 Q9 V– RC 50Ω COMP OUTPUT Q5 D1 Q15 Q10 Q11 SHUTDOWN V+ V+ Q3 Q4 Q7 Q8 D2 Q13 Q12 Q16 Q14 V– 1206 SS applicaTions inForMaTion The LT1206 is a current feedback amplifier with high output current drive capability. The device is stable with large capacitive loads and can easily supply the high currents required by capacitive loads. The amplifier will drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The optimum value for the feedback resistors is a function of the operating conditions of the device, the load impedance and the desired flatness of response. The Typical AC Performance tables give the values which result in the highest 0.1dB and 0.5dB bandwidths for various resistive loads and operating conditions. If this level of flatness is not required, a higher bandwidth can be obtained by use of a lower feedback resistor. The characteristic curves of Bandwidth vs Supply Voltage indicate feedback resistors for peaking up to 5dB. These curves use a solid line when the response has less than 0.5dB of peaking and a dashed line when the response has 0.5dB to 5dB of peaking. The curves stop where the response has more than 5dB of peaking. For resistive loads, the COMP pin should be left open (see section on capacitive loads). Capacitive Loads The LT1206 includes an optional compensation network for driving capacitive loads. This network eliminates most of the output stage peaking associated with capacitive loads, allowing the frequency response to be flattened. Figure 1 shows the effect of the network on a 200pF load. Without the optional compensation, there is a 5dB peak at 40MHz caused by the effect of the capacitance on the output stage. Adding a 0.01µF bypass capacitor between the output and the COMP pins connects the compensation and completely eliminates the peaking. A lower value feedback resistor can now be used, resulting in a response which 1206fb 8 LT1206 applicaTions inForMaTion 12 10 8 VOLTAGE GAIN (dB) 6 4 2 0 –2 –4 –6 –8 1 10 FREQUENCY (MHz) 100 1206 F01 VS = ±15V RF = 1.2k COMPENSATION RF = 2k NO COMPENSATION RF = 2k COMPENSATION Figure 1 is flat to 0.35dB to 30MHz. The network has the greatest . effect for CL in the range of 0pF to 1000pF The graph of Maximum Capacitive Load vs Feedback Resistor can be used to select the appropriate value of feedback resistor. The values shown are for 0.5dB and 5dB peaking at a gain of 2 with no resistive load. This is a worst case condition, as the amplifier is more stable at higher gains and with some resistive load in parallel with the capacitance. Also shown is the – 3dB bandwidth with the suggested feedback resistor vs the load capacitance. Although the optional compensation works well with capacitive loads, it simply reduces the bandwidth when it is connected with resistive loads. For instance, with a 30Ω load, the bandwidth drops from 55MHz to 35MHz when the compensation is connected. Hence, the compensation was made optional. To disconnect the optional compensation, leave the COMP pin open. Shutdown/Current Set If the shutdown feature is not used, the SHUTDOWN pin must be connected to ground or V –. The shutdown pin can be used to either turn off the biasing for the amplifier, reducing the quiescent current to less than 200µA, or to control the quiescent current in normal operation. The total bias current in the LT1206 is controlled by the current flowing out of the shutdown pin. When the shutdown pin is open or driven to the positive supply, the part is shut down. In the shutdown mode, the output looks like a 40pF capacitor and the supply current is typically 100µA. The shutdown pin is referenced to the positive supply through an internal bias circuit (see the simplified schematic). An easy way to force shutdown is to use open drain (collector) logic. The circuit shown in Figure 2 uses a 74C904 buffer to interface between 5V logic and the LT1206. The switching time between the active and shutdown states is less than 1µs. A 24k pull-up resistor speeds up the turn-off time and insures that the LT1206 is completely turned off. Because the pin is referenced to the positive supply, the logic used should have a breakdown voltage of greater than the positive supply voltage. No other circuitry is necessary as the internal circuit limits the shutdown pin current to about 500µA. Figure 3 shows the resulting waveforms. 15V VIN + LT1206 VOUT – S/D –15V RF 15V 5V ENABLE 74C906 24k RG 1206 F02 Figure 2. Shutdown Interface VOUT ENABLE AV = 1 RF = 825Ω RL = 50Ω RPU = 24k VIN = 1VP-P 1µs/DIV 1206 F03 Figure 3. Shutdown Operation 1206fb 9 LT1206 applicaTions inForMaTion For applications where the full bandwidth of the amplifier is not required, the quiescent current of the device may be reduced by connecting a resistor from the shutdown pin to ground. The quiescent current will be approximately 40 times the current in the shutdown pin. The voltage across the resistor in this condition is V + – 3VBE. For example, a 60k resistor will set the quiescent supply current to 10mA with VS = ±15V. The photos (Figures 4a and 4b) show the effect of reducing the quiescent supply current on the large-signal response. The quiescent current can be reduced to 5mA in the inverting configuration without much change in response. In noninverting mode, however, the slew rate is reduced as the quiescent current is reduced. Slew Rate Unlike a traditional op amp, the slew rate of a current feedback amplifier is not independent of the amplifier gain configuration. There are slew rate limitations in both the input stage and the output stage. In the inverting mode, and for higher gains in the noninverting mode, the signal amplitude on the input pins is small and the overall slew rate is that of the output stage. The input stage slew rate is related to the quiescent current and will be reduced as the supply current is reduced. The output slew rate is set by the value of the feedback resistors and the internal capacitance. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way the bandwidth is reduced. The photos (Figures 5a, 5b and 5c) show the large-signal response of the LT1206 for various gain configurations. The slew rate varies from 860V/µs for a gain of 1, to 1400V/µs for a gain of – 1. RF = 750Ω RL = 50Ω IQ = 5mA, 10mA, 20mA VS = ±15V 50ns/DIV 1206 F04a Figure 4a. Large-Signal Response vs IQ, AV = –1 RF = 825Ω RL = 50Ω VS = ±15V 20ns/DIV 1206 F05a Figure 5a. Large-Signal Response, AV = 1 RF = 750Ω RL = 50Ω IQ = 5mA, 10mA, 20mA VS = ±15V 50ns/DIV 1206 F04b Figure 4b. Large-Signal Response vs IQ, AV = 2 RF = RG = 750Ω RL = 50Ω VS = ±15V 20ns/DIV 1206 F05b Figure 5b. Large-Signal Response, AV = –1 1206fb 10 LT1206 applicaTions inForMaTion the maximum allowable input voltage. To allow for some margin, it is recommended that the input signal be less than ±5V when the device is shut down. Capacitance on the Inverting Input Current feedback amplifiers require resistive feedback from the output to the inverting input for stable operation. Take care to minimize the stray capacitance between the output and the inverting input. Capacitance on the inverting input to ground will cause peaking in the frequency response (and overshoot in the transient response), but it does not degrade the stability of the amplifier. Power Supplies The LT1206 will operate from single or split supplies from ± 5V (10V total) to ±15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage and inverting input bias current will change. The offset voltage changes about 500µV per volt of supply mismatch. The inverting bias current can change as much as 5µA per volt of supply mismatch, though typically the change is less than 0.5µA per volt. Thermal Considerations The LT1206 contains a thermal shutdown feature which protects against excessive internal (junction) temperature. If the junction temperature of the device exceeds the protection threshold, the device will begin cycling between normal operation and an off state. The cycling is not harmful to the part. The thermal cycling occurs at a slow rate, typically 10ms to several seconds, which depends on the power dissipation and the thermal time constants of the package and heat sinking. Raising the ambient temperature until the device begins thermal shutdown gives a good indication of how much margin there is in the thermal design. For surface mount devices heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PCB material can be very effective at transmitting heat between the pad area attached to the tab of the device, and a ground or 1206fb RF = 750Ω RL = 50Ω 20ns/DIV 1206 F05c Figure 5c. Large-Signal Response, AV = 2 When the LT1206 is used to drive capacitive loads, the available output current can limit the overall slew rate. In the fastest configuration, the LT1206 is capable of a slew rate of over 1V/ns. The current required to slew a capacitor at this rate is 1mA per picofarad of capacitance, so 10,000pF would require 10A! The photo (Figure 6) shows . the large signal behavior with CL = 10,000pF The slew rate is about 60V/µs, determined by the current limit of 600mA. VS = ±15V RL = RG = 3k RL = ∞ 500ns/DIV 1206 G06 Figure 6. Large-Signal Response, CL = 10,000pF Differential Input Signal Swing The differential input swing is limited to about ± 6V by an ESD protection device connected between the inputs. In normal operation, the differential voltage between the input pins is small, so this clamp has no effect; however, in the shutdown mode the differential swing can be the same as the input swing. The clamp voltage will then set 11 LT1206 applicaTions inForMaTion power plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PCB material is high, the length/area ratio of the thermal resistance between the layer is small. Copper board stiffeners and plated through holes can also be used to spread the heat generated by the device. Tables 1 and 2 list thermal resistance for each package. For the TO-220 package, thermal resistance is given for junction-to-case only since this package is usually mounted to a heat sink. Measured values of thermal resistance for several different board sizes and copper areas are listed for each surface mount package. All measurements were taken in still air on 3/32" FR-4 board with 1oz copper. This data can be used as a rough guideline in estimating thermal resistance. The thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape. Table 1. R Package, 7-Lead DD COPPER AREA TOPSIDE* BACKSIDE THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 330Ω Calculating Junction Temperature The junction temperature can be calculated from the equation: TJ = (PD × θJA) + TA where: TJ = Junction Temperature TA = Ambient Temperature PD = Device Dissipation θJA = Thermal Resistance (Junction-to Ambient) As an example, calculate the junction temperature for the circuit in Figure 7 for the N8, S8, and R packages assuming a 70°C ambient temperature. 15V I 39mA + – LT1206 S/D 0.01µF f = 2MHz 2k 300pF 12V –12V 2500 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 2500 sq. mm 125 sq. mm 2500 sq. mm 2500 sq. mm *Tab of device attached to topside copper. Table 2. S8 Package, 8-Lead Plastic SO COPPER AREA TOPSIDE* BACKSIDE 25°C/W 27°C/W 35°C/W –15V 2k 1206 F07 Figure 7. Thermal Calculation Example THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 2500 sq. mm 225 sq. mm 2500 sq. mm 2500 sq. mm 100 sq. mm 2500 sq. mm 2500 sq. mm 100 sq. mm 1000 sq. mm 2500 sq. mm 100 sq. mm 225 sq. mm 2500 sq. mm 100 sq. mm 100 sq. mm 2500 sq. mm *Pins 1 and 8 attached to topside copper. Y Package, 7-Lead TO-220 Thermal Resistance (Junction-to-Case) = 5°C/W N8 Package, 8-Lead DIP Thermal Resistance (Junction-to-Ambient) = 100°C/W 60°C/W 62°C/W 65°C/W 69°C/W 73°C/W 80°C/W 83°C/W The device dissipation can be found by measuring the supply currents, calculating the total dissipation, and then subtracting the dissipation in the load and feedback network. PD = (39mA × 30V) – (12V)2/(2k||2k) = 1.03W Then: TJ = (1.03W × 100°C/W) + 70°C = 173°C for the N8 package. TJ = (1.03W × 65°C/W) × + 70°C = 137°C for the S8 with 225 sq. mm topside heat sinking. TJ = (1.03W × 35°C/W) × + 70°C = 106°C for the R package with 100 sq. mm topside heat sinking. Since the maximum junction temperature is 150°C, the N8 package is clearly unacceptable. Both the S8 and R packages are usable. 1206fb 12 LT1206 applicaTions inForMaTion Precision ×10 Hi Current Amplifier VIN CMOS Logic to Shutdown Interface 15V + LT1097 – 500pF 330 LT1206 COMP – S/D + + OUT 0.01µF 5V 10k – LT1206 S/D 1206 TA03 24k 3k 10k –15V 2N3904 OUTPUT OFFSET: < 500µV SLEW RATE: 2V/µs BANDWIDTH: 4MHz STABLE WITH CL < 10nF 1206 TA02 1k Low Noise ×10 Buffered Line Driver 15V 1µF 15V 1µF Distribution Amplifier + LT1115 + + + 1µF + LT1206 S/D OUTPUT 0.01µF RL VIN 75 + – LT1206 S/D RF 75 75 CABLE – –15V 75 75 1206 TA05 – 560 909 – 15V 560 100 RL = 32 VO = 5VRMS THD + NOISE = 0.0009% AT 1kHz = 0.004% AT 20kHz SMALL SIGNAL 0.1dB BANDWIDTH = 600kHz VIN + – LT1206 COMP S/D + 1206 TA04 68pF 1µF RG 75 Buffer AV = 1 VOUT 0.01µF* RF** 1206 TA06 *OPTIONAL, USE WITH CAPACITIVE LOADS **VALUE OF RF DEPENDS ON SUPPLY VOLTAGE AND LOADING. SELECT FROM TYPICAL AC PERFORMANCE TABLE OR DETERMINE EMPIRICALLY 1206fb 13 LT1206 package DescripTion N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 .255 ± .015* (6.477 ± 0.381) 1 .300 – .325 (7.620 – 8.255) 2 3 4 .130 ± .005 (3.302 ± 0.127) .045 – .065 (1.143 – 1.651) .008 – .015 (0.203 – 0.381) +.035 .325 –.015 8.255 +0.889 –0.381 .065 (1.651) TYP ( ) .100 (2.54) BSC .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 1002 INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) NOTE: 1. DIMENSIONS ARE 1206fb 14 LT1206 package DescripTion R Package 7-Lead R Package Pak Plastic DD (Reference7-Lead Plastic DD Pak Rev E) LTC DWG # 05-08-1462 (Reference LTC DWG # 05-08-1462 Rev E) .256 (6.502) .060 (1.524) .060 (1.524) TYP .390 – .415 (9.906 – 10.541) 15° TYP .165 – .180 (4.191 – 4.572) .045 – .055 (1.143 – 1.397) .060 (1.524) .183 (4.648) .330 – .370 (8.382 – 9.398) .059 (1.499) TYP ( +.008 .004 –.004 +0.203 0.102 –0.102 ) .075 (1.905) .300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +.012 .143 –.020 +0.305 3.632 –0.508 .050 (1.27) BSC .013 – .023 (0.330 – 0.584) .095 – .115 (2.413 – 2.921) .050 ± .012 (1.270 ± 0.305) ( ) .026 – .035 (0.660 – 0.889) TYP .420 .080 .420 .276 .350 .205 .585 .325 .585 .320 .090 .050 .035 .050 .090 .035 RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS R (DD7) 0710 REV E 1206fb 15 LT1206 package DescripTion S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .045 ±.005 8 .189 – .197 (4.801 – 5.004) NOTE 3 7 6 5 .050 BSC .245 MIN .160 ±.005 .228 – .244 (5.791 – 6.197) .150 – .157 (3.810 – 3.988) NOTE 3 .030 ±.005 TYP RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 0°– 8° TYP 1 2 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) .014 – .019 (0.355 – 0.483) TYP .050 (1.270) BSC SO8 0303 T7 Package 7-Lead Plastic TO-220 (Standard) (Reference LTC DWG # 05-08-1422) .147 – .155 (3.734 – 3.937) DIA .230 – .270 (5.842 – 6.858) .460 – .500 (11.684 – 12.700) .570 – .620 (14.478 – 15.748) .330 – .370 (8.382 – 9.398) .620 (15.75) TYP .165 – .180 (4.191 – 4.572) .390 – .415 (9.906 – 10.541) .045 – .055 (1.143 – 1.397) .700 – .728 (17.780 – 18.491) SEATING PLANE .152 – .202 .260 – .320 (3.860 – 5.130) (6.604 – 8.128) BSC .050 (1.27) .026 – .036 (0.660 – 0.914) .095 – .115 (2.413 – 2.921) .155 – .195* (3.937 – 4.953) .013 – .023 (0.330 – 0.584) *MEASURED AT THE SEATING PLANE T7 (TO-220) 0801 .135 – .165 (3.429 – 4.191) 1206fb 16 LT1206 revision hisTory REV B DATE 3/11 DESCRIPTION Updated note on Table 2 in the Applications Information section. (Revision history begins at Rev B) PAGE NUMBER 12 1206fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 17 LT1206 relaTeD parTs PART NUMBER LT1010 LT1207 LT1210 LT1395 LT1815 LT1818 DESCRIPTION High Speed Buffer Dual 250mA Out, 900V/µs, 60MHz Current Feedback Amplifier 1.1A, 35MHz, 900V/µs Current Feedback Amplifier Single 400MHz Current Feedback Amplifier 6.5mA, 220MHz, 1.5V/ns Operational Amplifier with Programmable Current 400MHz, 2500V/µs, 9mA Single Operational Amplifier COMMENTS High Power, High Speed Buffer Adjustable Supply Current, Shutdown Adjustable Supply Current, Shutdown 0.1dB Gain Flatness to 100MHz S6 Version Features Programmable Supply Current High Speed, Low Noise, Low Distortion, Low Offset 1206fb 18 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● LT 0311 REV B • PRINTED IN USA www.linear.com  LINEAR TECHNOLOGY CORPORATION 1993