LT1227C

LT1227 140MHz Video Current Feedback Amplifier FEATURES s s s s s s s s s s s s DESCRIPTIO 140MHz Bandwidth: AV = 2, RL = 150Ω 1100V/µs Slew Rate Low Cost 30mA Output Drive Current 0.01% Differential Gain 0.01° Differential Phase High Input Impedance: 14MΩ, 3pF Wide Supply Range: ± 2V to ±15V Shutdown Mode: IS < 250µA Low Supply Current: IS = 10mA Inputs Common Mode to Within 1.5V of Supplies Outputs Swing Within 0.8V of Supplies The LT1227 is a current feedback amplifier with wide bandwidth and excellent video characteristics. The low differential gain and phase, wide bandwidth, and 30mA output drive current make the LT1227 well suited to drive cables in video systems. A shutdown feature switches the device into a high impedance, low current mode, allowing multiple devices to be connected in parallel and selected. Input to output isolation in shutdown is 70dB at 10MHz for input amplitudes up to 10VP-P. The shutdown pin interfaces to open collector or open drain logic and takes only 4µs to enable or disable. The LT1227 comes in the industry standard pinout and can upgrade the performance of many older products. For a dual or quad version, see the LT1229/1230 data sheet. The LT1227 is manufactured on Linear Technology’s proprietary complementary bipolar process. APPLICATI s s s s s S Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers 50Ω Buffers for Driving Mixers TYPICAL APPLICATI Video Cable Driver 0.20 Differential Gain and Phase vs Supply Voltage 0.20 NTSC COMPOSITE f = 3.58MHz VIN + LT1227 75Ω DIFFERENTIAL PHASE (DEG) 0.16 – RF 1k 75Ω CABLE VOUT 0.12 0.08 ∆φ 0.04 ∆G 0 5 7 11 13 9 SUPPLY VOLTAGE (±V) 15 RG 1k VOUT =1 VIN 75Ω 1227 TA01 U 0.16 UO UO DIFFERENTIAL GAIN (%) 0.12 0.08 0.04 0 LT1227 • TA02 1 LT1227 ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW NULL 1 –IN 2 +IN 3 V – Supply Voltage ..................................................... ±18V Input Current ...................................................... ±15mA Output Short Circuit Duration (Note 1) ........ Continuous Operating Temperature Range LT1227C .................................................. 0°C to 70°C LT1227M ......................................... – 55°C to 125°C Storage Temperature Range ................. – 65°C to 150°C Junction Temperature Plastic Package ................................................ 150°C Ceramic Package ............................................. 175°C Lead Temperature (Soldering, 10 sec.)................ 300°C 8 SHUTDOWN 7 V+ 6 OUT 5 NULL ORDER PART NUMBER LT1227MJ8 LT1227CN8 4 N8 PACKAGE J8 PACKAGE 8-LEAD CERAMIC DIP 8-LEAD PLASTIC DIP TJMAX = 175°C, θJA = 100° C/W (J) TJMAX = 150°C, θJA = 100°C/W (N) TOP VIEW NULL 1 –IN 2 +IN 3 V– 4 8 SHUTDOWN 7 V+ 6 OUT LT1227CS8 S8 PART MARKING 1227 5 NULL S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 150°C/W Consult factory for Industrial grade parts. ELECTRICAL CHARACTERISTICS SYMBOL VOS PARAMETER Input Offset Voltage Input Offset Voltage Drift Noninverting Input Current Inverting Input Current Input Noise Voltage Density Noninverting Input Noise Current Density Inverting Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range VCM = 0, ± 5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted. MIN q q CONDITIONS TA = 25°C TYP ±3 10 ± 0.3 ±10 MAX ±10 ±15 ±3 ±10 ±60 ±100 IIN+ IIN– en +in –in RIN CIN TA = 25°C q TA = 25°C q f = 1kHz, RF = 1k, RG = 10Ω, RS = 0Ω f = 1kHz f = 1kHz VIN = ±13V, VS = ±15V VIN = ± 3V, VS = ± 5V VS = ±15V, TA = 25°C q q 1.5 1.5 ±13 ±12 ±3 ±2 55 55 55 55 3.2 1.7 32 14 11 3 ±13.5 ± 3.5 62 61 3.5 10 10 10 10 q VS = ±5V, TA = 25°C q CMRR Common-Mode Rejection Ratio Inverting Input Current Common-Mode Rejection VS = ±15V, VCM = ±13V, TA = 25°C VS = ±15V, VCM = ±12V VS = ±5V, VCM = ± 3V, TA = 25°C VS = ± 5V, VCM = ±2V VS = ±15V, VCM = ±13V, TA = 25°C VS = ±15V, VCM = ±12V VS = ±5V, VCM = ± 3V, TA = 25°C VS = ± 5V, VCM = ±2V q q q 4.5 q UNITS mV mV µV/°C µA µA µA µA nV/√Hz pA/√Hz pA/√Hz MΩ MΩ pF V V V V dB dB dB dB µA/V µA/V µA/V µA/V 2 U W U U WW W LT1227 ELECTRICAL CHARACTERISTICS SYMBOL PSRR PARAMETER Power Supply Rejection Ratio Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection Large-Signal Voltage Gain Transresistance, ∆VOUT/∆IIN– Maximum Output Voltage Swing VCM = 0, ± 5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted. MIN 60 60 TYP 80 2 q AV ROL VOUT CONDITIONS VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±15V, VOUT = ±10V, RL = 1k VS = ±5V, VOUT = ± 2V, RL = 150Ω VS = ±15V, VOUT = ±10V, RL = 1k VS = ±5V, VOUT = ± 2V, RL = 150Ω VS = ±15V, RL = 400Ω, TA = 25°C VS = ±5V, RL = 150Ω, TA = 25°C MAX q 0.25 q q q q q q q 50 50 5 5 IOUT IS Maximum Output Current Supply Current (Note 2) Positive Supply Current, Shutdown RL = 0Ω, TA = 25°C VS = ±15V, VOUT = 0V, TA = 25°C q 55 55 100 100 ±12 ±10 ±3 ± 2.5 30 72 72 270 240 ±13.5 ± 3.7 60 10 120 VS = ±15V, Pin 8 Voltage = 0V, TA = 25°C q I8 SR tr, tf BW tr, tf tS Shutdown Pin Current (Note 3) Output Leakage Current, Shutdown Slew Rate (Notes 4 and 5) Rise and Fall Time, VOUT = 1VP-P Small-Signal Bandwidth Small-Signal Rise and Fall Time Propagation Delay Small-Signal Overshoot Settling Time Differential Gain (Note 6) Differential Phase (Note 6) VS = ±15V VS = ±15V, Pin 8 Voltage = 0V, TA = 25°C TA = 25°C VS = ±5V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω 0.1%, VOUT = 10V, RF = 1k, RG = 1k, RL = 1k VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 1k VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 1k q 15.0 17.5 300 500 300 10 500 1100 8.7 140 3.3 3.4 5 50 0.014 0.010 0.010 0.013 UNITS dB dB nA/V nA/V µA/V µA/V dB dB kΩ kΩ V V V V mA mA mA µA µA µA µA V/µs ns MHz ns ns % ns % % DEG DEG The q denotes specifications which apply over the operating temperature range. Note 1: A heat sink may be required depending on the power supply voltage. Note 2: The supply current of the LT1227 has a negative temperature coefficient. For more information, see Typical Performance Characteristics curves. Note 3: Ramp pin 8 voltage down from 15V while measuring IS. When IS drops to less than 0.5mA, measure pin 8 current. Note 4: Slew rate is measured at ± 5V on a ±10V output signal while operating on ±15V supplies with RF = 2k, RG = 220Ω and R L = 400Ω. Note 5: AC parameters are 100% tested on the ceramic and plastic DIP package parts (J and N suffix) and are sample tested on every lot of the SO packaged parts (S suffix). Note 6: NTSC composite video with an output level of 2V. 3 LT1227 TYPICAL PERFOR A CE CHARACTERISTICS Voltage Gain and Phase vs Frequency, Gain = 6dB 10 9 8 PHASE 0 –3dB BANDWIDTH (MHz) VOLTAGE GAIN (dB) 7 6 5 4 3 2 1 0 0.1 VS = ±15V RL = 100Ω RF = 910Ω 1 10 FREQUENCY (MHz) 100 LT1227 • TPC01 135 GAIN 180 225 120 100 80 60 40 20 0 RF = 500Ω RF = 750Ω RF = 1k –3dB BANDWIDTH (MHz) Voltage Gain and Phase vs Frequency, Gain = 20dB 24 23 22 PHASE 0 VOLTAGE GAIN (dB) 21 20 19 18 17 16 15 14 0.1 VS = ±15V RL = 100Ω RF = 825Ω 1 10 FREQUENCY (MHz) 100 LT1227 • TPC04 135 GAIN 180 225 –3dB BANDWIDTH (MHz) –3dB BANDWIDTH (MHz) Voltage Gain and Phase vs Frequency, Gain = 40dB 44 43 42 PHASE 0 –3dB BANDWIDTH (MHz) VOLTAGE GAIN (dB) 41 40 39 38 37 36 35 34 0.1 VS = ±15V RL = 100Ω RF = 500Ω 1 10 FREQUENCY (MHz) 100 LT1227 • TPC07 135 GAIN 180 225 12 10 8 6 4 2 0 0 2 4 RF = 500Ω RF = 1k RF = 2k –3dB BANDWIDTH (MHz) 4 UW –3dB Bandwidth vs Supply Voltage, Gain = 2, RL = 100Ω 180 160 140 PEAKING ≤ 0.5dB PEAKING ≤ 5dB 180 160 140 120 100 80 60 40 20 16 0 18 –3dB Bandwidth vs Supply Voltage, Gain = 2, RL = 1k PEAKING ≤ 0.5dB PEAKING ≤ 5dB RF = 750Ω RF = 2k RF = 1.5k RF = 1k PHASE SHIFT (DEG) PHASE SHIFT (DEG) PHASE SHIFT (DEG) 45 90 RF = 2k 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 LT1227 • TPC02 LT1227 • TPC03 –3dB Bandwidth vs Supply Voltage, Gain = 10, RL = 100Ω 180 160 140 120 100 80 60 40 20 0 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 RF = 2k RF = 250Ω RF = 500Ω RF = 750Ω RF = 1k PEAKING ≤ 0.5dB PEAKING ≤ 5dB –3dB Bandwidth vs Supply Voltage, Gain = 10, RL = 1k 180 160 140 120 100 80 60 40 20 0 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 RF = 2k RF = 750Ω RF = 1k RF = 500Ω PEAKING ≤ 0.5dB PEAKING ≤ 5dB 45 90 LT1227 • TPC05 LT1227 • TPC06 –3dB Bandwidth vs Supply Voltage, Gain = 100, RL = 100Ω 18 16 14 18 16 14 12 10 8 6 4 2 0 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 45 90 –3dB Bandwidth vs Supply Voltage, Gain = 100, RL = 1k RF = 500Ω RF = 1k RF = 2k 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 LT1227 • TPC08 LT1227 • TPC09 LT1227 TYPICAL PERFOR A CE CHARACTERISTICS Maximum Capacitive Load vs Feedback Resistor 10000 TOTAL HARMONIC DISTORTION (%) RL = 1k PEAKING ≤ 5dB GAIN = 2 CAPACITIVE LOAD (pF) OUTPUT VOLTAGE (VP-P) 1000 VS = ±5V 100 VS = ±15V 10 1 0 1 2 FEEDBACK RESISTOR (kΩ) 3 Input Common Mode Limit vs Temperature V+ OUTPUT SATURATION VOLTAGE (V) –0.5 COMMON MODE RANGE (V) –1.0 –1.5 –2.0 V + = 2V TO 18V –0.5 –1.0 OUTPUT SHORT-CIRCUIT CURRENT (mA) 2.0 1.5 1.0 0.5 V– –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 V – = – 2V TO –18V Spot Noise Voltage and Current vs Frequency 100 POWER SUPPLY REJECTION (dB) 80 SPOT NOISE (nV/√Hz OR pA/√Hz) POSITIVE NEGATIVE 40 OUTPUT IMPEDANCE (Ω) –in 10 en +in 1 10 100 1k 10k FREQUENCY (Hz) UW LT1227 • TPC10 Total Harmonic Distortion vs Frequency 0.1 VS = ±15V RL = 400Ω RF = RG = 1k 25 Maximum Undistorted Output vs Frequency VS = ±15V RL = 1k RF = 1k AV = +10 AV = –1 AV = +1 AV = +2 20 15 0.01 VO = 7VRMS 10 VO = 1VRMS 5 0.001 10 0 100 1k 10k FREQUENCY (Hz) 100k LT1227 • TPC11 1 10 FREQUENCY (MHz) 100 LT1127 • TPC12 Output Saturation Voltage vs Temperature V+ RL = ∞ ±2V ≤ VS ≤ ±18V 70 Output Short-Circuit Current vs Junction Temperature 60 50 1.0 0.5 V– –50 –25 40 50 25 75 0 TEMPERATURE (°C) 100 125 30 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1227 • TPC15 LT1227 • TPC13 LT1227 • TPC14 Power Supply Rejection vs Frequency 100 VS = ±15V RL = 100Ω RF = RG = 1k 60 Output Impedance vs Frequency VS = ±15V 10 RF = RG = 2k RF = RG = 1k 0.1 1 20 0.01 100k LT1227 • TPC16 0 10k 100k 1M 10M FREQUENCY (Hz) 100M LT1227 • TPC17 0.001 10k 100k 1M 10M FREQUENCY (Hz) 100M LT1227 • TPC18 5 LT1227 TYPICAL PERFOR A CE CHARACTERISTICS Settling Time to 10mV vs Output Step 10 8 6 OUTPUT STEP (V) 10 VS = ±15V RF = RG = 1k SUPPLY CURRENT (mA) NONINVERTING INVERTING OUTPUT STEP (V) 4 2 0 –2 –4 –6 –8 –10 0 20 60 40 SETTLING TIME (ns) Output Impedance in Shutdown vs Frequency 100 VS = ±15V AV = 1 RF = 1.5k 10 0 0.05 0.10 0.15 0.20 0.25 0.1 100k DIFFERENTIAL PHASE (DEG) OUTPUT IMPEDANCE (kΩ) DIFFERENTIAL GAIN (%) 1 1M 10M FREQUENCY (Hz) 2nd and 3rd Harmonic Distortion vs Frequency –20 VS = ±15V VO = 2VP-P RL = 100Ω RF = 820Ω AV = 10dB 2ND 3RD –30 3RD ORDER INTERCEPT (dBm) DISTORTION (dBc) –40 –50 –60 –70 1 10 FREQUENCY (MHz) 100 LT1227 • TPC25 6 UW 80 LT1227 • TPC19 LT1227 • TPC22 Settling Time to 1mV vs Output Step 14 VS = ±15V RF = RG = 1k 8 6 4 2 0 –2 –4 –6 –8 –10 NONINVERTING INVERTING Supply Current vs Supply Voltage 13 12 11 10 9 8 7 6 5 4 125°C 175°C –55°C 25°C 100 0 4 12 16 8 SETTLING TIME (µs) 20 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 LT1227 • TPC20 LT1227 • TPC21 Differential Phase vs Frequency 0 (VO)DC = 0.5V 1.0V 1.5V 2.0V 0.01 0.02 0.03 0.04 0.05 Differential Gain vs Frequency (VO)DC = 0.5V 1.0V 2.0V VS = ±15V AV = 2 RL = 1k RF = 1k RG = 1k 1M 10M 100M LT1227 • TPC24 100M 0.30 100k VS = ±15V AV = 2 RL = 1k RF = 1k RG = 1k 1M 10M 100M LT1227 • TPC23 0.06 100k FREQUENCY (Hz) FREQUENCY (Hz) 3rd Order Intercept vs Frequency 45 40 35 30 25 20 15 0 10 20 30 40 FREQUENCY (MHz) 50 60 VS = ±15V RL = 100Ω RF = 680Ω RG = 75Ω Test Circuit for 3rd Order Intercept + LT1227 50Ω PO – 680Ω 75Ω MEASURE INTERCEPT AT PO 50Ω 1227 TC LT1227 • TPC26 LT1227 SI PLIFIED SCHE ATIC 7 V+ 14k CURRENT SOURCE BIAS 8 S/D +IN 3 2 –IN 6 VOUT APPLICATI S I FOR ATIO The LT1227 is a very fast current feedback amplifier. Because it is a current feedback amplifier, the bandwidth is maintained over a wide range of voltage gains. The amplifier is designed to drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The small-signal bandwidth of the LT1227 is set by the external feedback resistors and the internal junction capacitors. As a result, the bandwidth is a function of the supply voltage, the value of the feedback resistor, the closed-loop gain and load resistor. The characteristic curves of Bandwidth vs Supply Voltage show the effect of a heavy load (100Ω) and a light load (1k). 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 U W W U UO W NULL 1 NULL 5 4 V– 1227 SS 5dB of peaking. The curves stop where the response has more than 5dB of peaking. At a gain of two, on ±15V supplies with a 1k feedback resistor, the bandwidth into a light load is over 140MHz, but into a heavy load the bandwidth reduces to 120MHz. The loading has this effect because there is a mild resonance in the output stage that enhances the bandwidth at light loads but has its Q reduced by the heavy load. This enhancement is only useful at low gain settlings; at a gain of ten it does not boost the bandwidth. At unity gain, the enhancement is so effective the value of the feedback resistor has very little effect. At very high closed-loop gains, the bandwidth is limited by the gain bandwidth product of about 1GHz. The curves show that the bandwidth at a closed-loop gain of 100 is 12MHz, only one tenth what it is at a gain of two. 7 LT1227 APPLICATI S I FOR ATIO Small-Signal Rise Time, AV = +2 VOUT RF = 1k, RG= 1k, RL = 100Ω 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. Capacitive Loads The LT1227 can drive capacitive loads directly when the proper value of feedback resistor is used. The graph of Maximum Capacitive Load vs Feedback Resistor should be used to select the appropriate value. The value shown is for 5dB peaking when driving a 1k load at a gain of 2. This is a worst case condition, the amplifier is more stable at higher gains and driving heavier loads. Alternatively, a small resistor (10Ω to 20Ω) can be put in series with the output to isolate the capacitive load from the amplifier output. This has the advantage that the amplifier bandwidth is only reduced when the capacitive load is present and the disadvantage that the gain is a function of the load resistance. Power Supplies The LT1227 will operate from single or split supplies from ±2V (4V total) to ±15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage 8 U 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 5.0µA per volt of supply mismatch, though typically the change is less than 0.5µA per volt. Slew Rate The slew rate of a current feedback amplifier is not independent of the amplifier gain configuration the way slew rate is in a traditional op amp. This is because both the input stage and the output stage have slew rate limitations. In the inverting mode, and for higher gains in the noninverting mode, the signal amplitude between the input pins is small and the overall slew rate is that of the output stage. For gains less than ten in the noninverting mode, the overall slew rate is limited by the input stage. The input stage slew rate of the LT1227 is approximately 125V/µs and is set by internal currents and capacitances. The output slew rate is set by the value of the feedback resistors and the internal capacitances. At a gain of ten with a 1k feedback resistor and ±15V supplies, the output slew rate is typically 1100V/µs. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way the bandwidth is reduced. The graph of Maximum Undistorted Output vs Frequency relates the slew rate limitations to sinusoidal inputs for various gain configurations. Large-Signal Transient Response, AV = +10 AI01 W U UO VOUT RF = 910Ω, RG= 100Ω, RL = 400Ω AI02 LT1227 APPLICATI S I FOR ATIO Large-Signal Transient Response, AV = +2 VOUT RF = 1k, RG= 1k, RL = 400Ω Large-Signal Transient Response, AV = –2 VOUT RF = 1k, RG= 510Ω, RL = 400Ω Settling Time The characteristic curves show that the LT1227 amplifier settles to within 10mV of final value in 40ns to 55ns for any output step up to 10V. The curve of settling to 1mV of final value shows that there is a slower thermal contribution up to 20µs. The thermal settling component comes from the output and the input stage. The output contributes just under 1mV per volt of output change and the input contributes 300µV per volt of input change. Fortunately the input thermal tends to cancel the output thermal. For this reason the noninverting gain of two configuration settles faster than the inverting gain of one. U Shutdown The LT1227 has a high impedance, low supply current mode which is controlled by pin 8. In the shutdown mode, the output looks like a 12pF capacitor and the supply current drops to approximately the pin 8 current. The shutdown pin is referenced to the positive supply through an internal pullup circuit (see the simplified schematic). Pulling a current of greater than 50µA from pin 8 will put the device into the shutdown mode. An easy way to force shutdown is to ground pin 8, using open drain (collector) logic. 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 an internal JFET limits the pin 8 current to about 100µA. When pin 8 is open, the LT1227 operates normally. 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 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 shutdown. Offset Adjust Pins 1 and 5 are provided for offset nulling. A small current to V + or ground will compensate for DC offsets in the device. The pins are referenced to the positive supply (see the simplified schematic) and should be left open if unused. The offset adjust pins act primarily on the inverting input bias current. A 10k pot connected to pins 1 and 5 with the wiper connected to V + will null out the bias current, but will not affect the offset voltage much. Since the output offset is VO ≅ AV • VOS + (IIN –) • RF at higher gains (AV > 5), the VOS term will dominate. To null out the VOS term, use a 10k pot between pins 1 and 5 with a 150k resistor from the wiper to ground for 15V split supplies, 47k for 5V split supplies. AI03 AI04 AI04 W U UO 9 LT1227 TYPICAL APPLICATI MUX Amplifier The shutdown function can be effectively used to construct a MUX amplifier. A two-channel version is shown, but more inputs could be added with suitable logic. By configuring each amplifier as a unity-gain follower, there is no loading by the feedback network when the amplifier is off. The open drains of the 74C906 buffers are used to interface the 5V logic to the shutdown pin. Feedthrough from the unselected input to the output is –70dB at 10MHz. The differential voltage between MUX inputs VIN1 and VIN2 appears across the inputs of the shutdown device, this voltage should be less than ±5V to avoid turning on the clamp diodes discussed previously. If the inputs are sinusoidal having a zero DC level, this implies that the amplitude of each input should be less than 5VP-P. The output impedance of the off amplifier remains high until the output level exceeds approximately 6VP-P at 10MHz, this sets the maximum usable output level. Switching time between inputs is about 4µs without an external pullup. Adding a 10k pullup resistor from each shutdown pin to V + will reduce the switching time to 2µs but will increase the positive supply current in shutdown by 1.5mA. MUX Output MUX Input Crosstalk vs Frequency –40 VOUT INPUT CROSSTALK (dB) INPUT SELECT VIN1 = 1VP-P, VIN2 = 0V 10 UO S MUX Amplifier 15V VIN1 + LT1227 S/D VOUT – VOUT =1 VIN –15V 1.5k 5V 74C906 15V VIN2 + LT1227 S/D – –15V 1.5k 5V INPUT SELECT 5V 74HC04 74C906 1227 TA04 –50 –60 –70 –80 –90 TA03 1 10 FREQUENCY (MHz) 100 LT1227 TA05 LT1227 TYPICAL APPLICATI Single Supply AC-Coupled Amplifier Noninverting 5V 4.7µF + AV = 22µF 10k 510Ω ≈ 10 RS + 51Ω 10k BW = 14Hz to 60MHz VIN + 10k LT1227 VOUT 2.2µF + 10k + LT1227 VOUT – 220µF 51Ω 510Ω AV = 11 BW = 14Hz to 60MHz – RS VIN 1227 TA08 220µF 51Ω 510Ω 1227 TA09 Buffer with DC Nulling Loop 3.58MHz Oscillator 15V 100k 2N3904 100pF 75pF 3.579545MHz 150k 68pF 1k 15V 1N4148 V+ 180Ω 10k 0.1µF VIN 10k 2 3 180Ω 10k 5 + LT1227 1 6 + + VOUT – LT1227 + –15V 1227 TA10 CMOS Logic to Shutdown Interface 15V 3 7 + LT1227 6 8 4 2 – –15V 10k 5V UO S Single Supply AC-Coupled Amplifier Inverting 5V 4.7µF + + – 1.5k 51Ω VOUT 100k 0.01µF + 100k LT1097 – 0.01µF 1227 TA07 Optional Offset Nulling circuit RNULL V+ 3 7 10k 1 LT1227 2 1227 TA11 + – 4 V– 2N3904 6 RNULL = 47k FOR VS = ±5V RNULL = 150k FOR VS = ±15V 1227 TA12 5 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. 11 LT1227 PACKAGE DESCRIPTIO 0.290 – 0.320 (7.366 – 8.128) 0.008 – 0.018 (0.203 – 0.457) 0.385 ± 0.025 (9.779 ± 0.635) 0° – 15° 1 0.045 – 0.068 (1.143 – 1.727) 0.014 – 0.026 (0.360 – 0.660) 0.125 3.175 0.100 ± 0.010 MIN (2.540 ± 0.254) 2 3 4 CORNER LEADS OPTION (4 PLCS) NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP OR TIN PLATE LEADS. 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION J8 0293 0.300 – 0.320 (7.620 – 8.128) 0.009 – 0.015 (0.229 – 0.381) 0.065 (1.651) TYP 0.125 (3.175) MIN 0.020 (0.508) MIN ( +0.025 0.325 –0.015 +0.635 8.255 –0.381 ) 0.045 ± 0.015 (1.143 ± 0.381) 0.100 ± 0.010 (2.540 ± 0.254) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 0.053 – 0.069 (1.346 – 1.752) 0.016 – 0.050 0.406 – 1.270 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U J8 Package 8-Lead Ceramic DIP 0.200 (5.080) MAX 0.015 – 0.060 (0.381 – 1.524) 0.005 (0.127) MIN 0.405 (10.287) MAX 8 7 6 5 0.025 (0.635) RAD TYP 0.220 – 0.310 (5.588 – 7.874) N8 Package 8-Lead Plastic DIP 0.400 (10.160) MAX 8 7 6 5 0.045 – 0.065 (1.143 – 1.651) 0.130 ± 0.005 (3.302 ± 0.127) 0.250 ± 0.010 (6.350 ± 0.254) 1 2 3 4 0.018 ± 0.003 (0.457 ± 0.076) N8 0392 S8 Package 8-Lead Plastic SOIC 8 0.004 – 0.010 (0.101 – 0.254) 0.228 – 0.244 (5.791 – 6.197) 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC 1 0.189 – 0.197* (4.801 – 5.004) 7 6 5 0.150 – 0.157* (3.810 – 3.988) 2 3 4 SO8 0294 LT/GP 0394 5K REV A © LINEAR TECHNOLOGY CORPORATION 1994