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LT1210CT7#PBF

LT1210CT7#PBF

  • 厂商:

    LINEAR(凌力尔特)

  • 封装:

    TO220-7

  • 描述:

    1.1A,35MHz电流反馈放大器

  • 数据手册
  • 价格&库存
LT1210CT7#PBF 数据手册
LT1210 1.1A, 35MHz Current Feedback Amplifier FEATURES DESCRIPTION 1.1A Minimum Output Drive Current nn 35MHz Bandwidth, A = 2, R = 10Ω V L nn 900V/µs Slew Rate, A = 2, R = 10Ω V L nn High Input Impedance: 10MΩ nn Wide Supply Range: ± 5V to ±15V (TO-220 and DD Packages) nn Enhanced θ JA SO-16 Package for ±5V Operation nn Shutdown Mode: I < 200µA S nn Adjustable Supply Current nn Stable with C = 10,000pF L nn Operating Temperature Range: –40°C to 85°C nn Available in 7-Lead DD, TO-220 and nn 16-Lead SO Packages The LT®1210 is a current feedback amplifier with high output current and excellent large-signal characteristics. The combination of high slew rate, 1.1A output drive and ±15V operation enables the device to deliver significant power at frequencies in the 1MHz to 2MHz range. Short-circuit protection and thermal shutdown ensure the device’s ruggedness. The LT1210 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 and low supply 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. nn The LT1210 is available in the TO-220 and DD packages for operation with supplies up to ± 15V. For ±5V applications the device is also available in a low thermal resistance SO-16 package. APPLICATIONS Cable Drivers Buffers nn Test Equipment Amplifiers nn Video Amplifiers nn ADSL Drivers nn nn All registered trademarks and trademarks are the property of their respective owners. TYPICAL APPLICATION Twisted Pair Driver Total Harmonic Distortion vs Frequency 15V 4.7µF* –50 100nF RT 11Ω 2.5W + VIN LT1210 SD – T1** 1 4.7µF* –15V 100nF RL 100Ω 2.5W 3 845Ω + 274Ω TOTAL HARMONIC DISTORTION (dB) + –60 –70 RL = 12.5Ω –80 –90 –100 * TANTALUM ** MIDCOM 671-7783 OR EQUIVALENT 1210 TA01 VS = ±15V VOUT = 20VP-P AV = 4 RL = 10Ω RL = 50Ω 1k 10k 100k FREQUENCY (Hz) 1M 1210 TA02 Rev C Document Feedback For more information www.analog.com 1 LT1210 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage ...................................................... ± 18V Input Current........................................................ ±15mA Output Short-Circuit Duration (Note 2)...........................................Thermally Limited Operating Temperature Range (Note 3) LT1210C................................................–40°C to 85°C LT1210I.................................................–40°C to 85°C Specified Temperature Range (Note 4) LT1210C.................................................... 0°C to 70°C LT1210I.................................................–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 FRONT VIEW TAB IS V+ 7 6 5 4 3 2 1 OUT V– COMP V+ SHUTDOWN +IN –IN R PACKAGE 7-LEAD PLASTIC D TJMAX = 150°C, θJA = 25°C/WD V+ 1 16 V+ V+ 2 15 NC FRONT VIEW OUT 3 14 V– 7 6 5 4 3 2 1 V+ 4 13 COMP NC 5 12 SHUTDOWN –IN 6 11 +IN NC 7 10 NC V+ 8 9 TAB IS V+ V+ OUT V– COMP V+ SHUTDOWN +IN –IN T7 PACKAGE 7-LEAD TO-220 TJMAX = 150°C, θJC = 5°C/W S PACKAGE 16-LEAD PLASTIC SO TJMAX = 150°C, θJA = 40°C/W (Note 5) ORDER INFORMATION http://www.linear.com/product/LT1210#orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1210CR#PBF LT1210CR#TRPBF LT1210R 7-Lead Plastic DDPAK 0°C to 70°C LT1210IR#PBF LT1210IR#TRPBF LT1210R 7-Lead Plastic DDPAK –40°C to 85°C LT1210CS#PBF LT1210CS#TRPBF LT1210CS 16-Lead Plastic SOIC 0°C to 70°C LT1210CT7#PBF N/A LT1210CT7 7-Lead TO-220 0°C to 70°C Consult ADI Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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/. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. 2 Rev C For more information www.analog.com LT1210 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0V, ± 5V ≤ VS ≤ ± 15V, pulse tested, VSD = 0V, unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage CONDITIONS MIN TYP MAX UNITS ±3 ±15 ±20 mV mV l Input Offset Voltage Drift IIN+ 10 l Noninverting Input Current ±2 ±5 ±20 µA µA ±10 ±60 ±100 µA µA l IIN– Inverting Input Current µV/°C l en Input Noise Voltage Density f = 10kHz, RF = 1kΩ, RG = 10Ω, RS = 0Ω 3.0 nV/√Hz +in Input Noise Current Density f = 10kHz, RF = 1kΩ, RG = 10Ω, RS = 10kΩ 2.0 pA/√Hz –in Input Noise Current Density f = 10kHz, RF = 1kΩ, RG = 10Ω, RS = 10kΩ 40 pA/√Hz RIN Input Resistance VIN = ±12V, VS = ±15V VIN = ±2V, VS = ±5V CIN Input Capacitance VS = ±15V Input Voltage Range CMRR PSRR AV ROL VOUT l l 1.50 0.25 10 5 MΩ MΩ 2 pF VS = ±15V VS = ± 5V l l ±12 ±2 ±13.5 ±3.5 V V Common Mode Rejection Ratio VS = ± 15V, VCM = ±12V VS = ±5V, VCM = ±2V l l 55 50 62 60 dB dB Inverting Input Current Common Mode Rejection VS = ± 15V, VCM = ±12V VS = ± 5V, VCM = ±2V l l Power Supply Rejection Ratio VS = ± 5V to ±15V l Noninverting Input Current Power Supply Rejection VS = ± 5V to ±15V l 30 500 nA/V Inverting Input Current Power Supply Rejection VS = ± 5V to ±15V l 0.7 5 µA/V Large-Signal Voltage Gain TA = 25°C, VS = ± 15V, VOUT = ±10V, RL = 10Ω (Note 5) Transresistance, ∆VOUT/∆IIN– Maximum Output Voltage Swing 0.1 0.1 60 55 10 10 77 µA/V µA/V dB 71 dB VS = ± 15V, VOUT = ±8.5V, RL = 10Ω (Note 5) l 55 68 dB VS = ±5V, VOUT = ±2V, RL = 10Ω l 55 68 dB 100 260 kΩ 75 200 kΩ kΩ TA = 25°C, VS = ± 15V, VOUT = ±10V, RL = 10Ω (Note 5) VS = ± 15V, VOUT = ±8.5V, RL = 10Ω (Note 5) l VS = ±5V, VOUT = ±2V, RL = 10Ω l 75 200 ±11.5 l ±10.0 ±8.5 V V ±2.5 ±2.0 ±3.0 l V V l 1.1 2.0 A TA = 25°C, VS = ± 15V, RL = 10Ω (Note 5) TA = 25°C, VS = ± 5V, RL = 10Ω IOUT Maximum Output Current (Note 5) VS = ± 15V, RL = 1Ω IS Supply Current (Note 5) TA = 25°C, VS = ±15V, VSD = 0V 35 50 65 mA mA 15 30 mA l Supply Current, RSD = 51kΩ (Notes 5, 6) TA = 25°C, VS = ±15V Positive Supply Current, Shutdown VS = ± 15V, VSD = 15V l 200 µA Output Leakage Current, Shutdown VS = ± 15V, VSD = 15V l 10 µA Rev C For more information www.analog.com 3 LT1210 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0V, ± 5V ≤ VS ≤ ± 15V, pulse tested, VSD = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP SR Slew Rate (Note 7) Slew Rate (Note 5) TA = 25°C, AV = 2, RL = 400Ω TA = 25°C, AV = 2, RL = 10Ω 400 900 900 V/µs V/µs Differential Gain (Notes 5, 8) VS = ±15V, RF = 750Ω, RG = 750Ω, RL = 15Ω 0.3 % Differential Phase (Notes 5, 8) VS = ±15V, RF = 750Ω, RG = 750Ω, RL = 15Ω 0.1 DEG Small-Signal Bandwidth AV = 2, VS = ±15V, Peaking ≤ 1dB, RF = RG = 680Ω, RL = 100Ω 55 MHz AV = 2, VS = ± 15V, Peaking ≤ 1dB, RF = RG = 576Ω, RL = 10Ω 35 MHz BW 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: A heat sink may be required to keep the junction temperature below the Absolute Maximum rating. 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: The LT1210C/LT1210I are guaranteed functional over the temperature range of –40°C to 85°C. Note 4: The LT1210C is guaranteed to meet specified performance from 0°C to 70°C. The LT1210C is designed, characterized and expected to meet specified performance from –40°C to 85°C but not tested or QA sampled at these temperatures. The LT1210I is guaranteed to meet specified performance from –40°C to 85°C. 4 MAX UNITS Note 5: SO package is recommended for ±5V supplies only, as the power dissipation of the SO package limits performance on higher supplies. For supply voltages greater than ±5V, use the TO-220 or DD package. See Thermal Considerations in the Applications Information section for details on calculating junction temperature. If the maximum dissipation of the package is exceeded, the device will go into thermal shutdown. Note 6: RSD is connected between the Shutdown pin and ground. Note 7: Slew rate is measured at ±5V on a ±10V output signal while operating on ±15V supplies with RF = 1.5kΩ, RG = 1.5kΩ and RL = 400Ω. Note 8: NTSC composite video with an output level of 2V. Rev C For more information www.analog.com LT1210 SMALL-SIGNAL BANDWIDTH RSD = 0Ω, IS = 30mA, VS = ± 5V, Peaking ≤ 1dB RSD = 0Ω, IS = 35mA, VS = ± 15V, Peaking ≤ 1dB AV RL (Ω) RF (Ω) RG (Ω) – 3dB BW (MHz) AV RL (Ω) RF (Ω) RG (Ω) – 3dB BW (MHz) –1 150 30 10 549 590 619 549 590 619 52.5 39.7 26.5 –1 150 30 10 604 649 665 604 649 665 66.2 48.4 46.5 1 150 30 10 604 649 619 – – – 53.5 39.7 27.4 1 150 30 10 750 866 845 – – – 56.8 35.4 24.7 2 150 30 10 562 590 576 562 590 576 51.8 38.8 27.4 2 150 30 10 665 715 576 665 715 576 52.5 38.9 35.0 10 150 30 10 392 383 215 43.2 42.2 23.7 48.4 40.3 36.0 10 150 30 10 453 432 221 49.9 47.5 24.3 61.5 43.1 45.5 RSD = 7.5kΩ, IS = 15mA, VS = ± 5V, Peaking ≤ 1dB RSD = 47.5kΩ, IS = 18mA, VS = ± 15V, Peaking ≤ 1dB AV RL (Ω) RF (Ω) RG (Ω) – 3dB BW (MHz) AV RL (Ω) RF (Ω) RG (Ω) – 3dB BW (MHz) –1 150 30 10 562 619 604 562 619 604 39.7 28.9 20.5 –1 150 30 10 619 698 698 619 698 698 47.8 32.3 22.2 1 150 30 10 634 681 649 – – – 41.9 29.7 20.7 1 150 30 10 732 806 768 – – – 51.4 33.9 22.5 2 150 30 10 576 604 576 576 604 576 40.2 29.6 21.6 2 150 30 10 634 698 681 634 698 681 48.4 33.0 22.5 10 150 30 10 324 324 210 35.7 35.7 23.2 39.5 32.3 27.7 10 150 30 10 348 357 205 38.3 39.2 22.6 46.8 36.7 31.3 RSD = 15kΩ, IS = 7.5mA, VS = ± 5V, Peaking ≤ 1dB RSD = 82.5kΩ, IS = 9mA, VS = ± 15V, Peaking ≤ 1dB AV RL (Ω) RF (Ω) RG (Ω) – 3dB BW (MHz) AV RL (Ω) RF (Ω) RG (Ω) – 3dB BW (MHz) –1 150 30 10 536 549 464 536 549 464 28.2 20.0 15.0 –1 150 30 10 590 649 576 590 649 576 34.8 22.5 16.3 1 150 30 10 619 634 511 – – – 28.6 19.8 14.9 1 150 30 10 715 768 649 – – – 35.5 22.5 16.1 2 150 30 10 536 549 412 536 549 412 28.3 19.9 15.7 2 150 30 10 590 665 549 590 665 549 35.3 22.5 16.8 10 150 30 10 150 118 100 16.5 13.0 11.0 31.5 27.1 19.4 10 150 30 10 182 182 100 20.0 20.0 11.0 37.2 28.9 22.5 Rev C For more information www.analog.com 5 LT1210 TYPICAL PERFORMANCE CHARACTERISTICS Bandwidth vs Supply Voltage 50 AV = 2 RL = 100Ω RF = 470Ω 70 60 RF = 560Ω 50 RF = 750Ω 40 RF = 680Ω 30 RF = 1kΩ 20 40 RF = 750Ω RF = 1kΩ 20 RF = 2kΩ 10 16 0 18 4 16 14 12 10 8 SUPPLY VOLTAGE (±V) 6 –3dB BANDWIDTH (MHz) –3dB BANDWIDTH (MHz) 70 RF = 330Ω RF =390Ω 60 50 RF = 470Ω 40 RF = 680Ω 30 20 10 40 30 RF = 680Ω 20 10 14 12 10 8 SUPPLY VOLTAGE (±V) 6 16 0 18 RF = 560Ω RF = 1.5kΩ 4 14 12 10 8 SUPPLY VOLTAGE (±V) 6 Differential Phase vs Supply Voltage 0.5 DIFFERENTIAL GAIN (%) 0.4 RF = RG = 750Ω AV = 2 RL = 15Ω 0.2 RL = 50Ω 0.3 RL = 15Ω 0.2 RL = 50Ω RL = 30Ω 5 7 11 13 9 SUPPLY VOLTAGE (±V) 15 1210 G07 AV = +2 RL = ∞ VS = ±15V CCOMP = 0.01µF 1 0 5 7 1 10000 10 100 1000 CAPACITIVE LOAD (pF) 1210 G06 100 RL = 10Ω 0.1 0.1 10 FEEDBACK RESISTANCE Spot Noise Voltage and Current vs Frequency RF = RG = 750Ω AV = 2 RL = 10Ω 0.3 0 100 18 Differential Gain vs Supply Voltage 0.6 0.4 1k 1210 G05 1210 G04 0.5 16 100 BANDWIDTH RF = 1kΩ RF = 1.5kΩ 4 10k –3dB BANDWIDTH (MHz) 80 1 10000 10 100 1000 CAPACITIVE LOAD (pF) Bandwidth and Feedback Resistance vs Capacitive Load for Peaking ≤ 5dB AV = 10 RL = 10Ω PEAKING ≤ 1dB AV = 10 RL = 100Ω PEAKING ≤ 1dB PEAKING ≤ 5dB 90 1 1210 G03 Bandwidth vs Supply Voltage 50 100 DIFFERENTIAL PHASE (DEG) AV = 2 RL = ∞ VS = ±15V CCOMP = 0.01µF 1210 G02 Bandwidth vs Supply Voltage 6 FEEDBACK RESISTANCE 100 18 FEEDBACK RESISTANCE (Ω) 14 12 10 8 SUPPLY VOLTAGE (±V) 6 SPOT NOISE (nV/√Hz OR pA/√Hz) 4 1210 G01 0 10 1k RF = 1.5kΩ 10 0 BANDWIDTH RF = 560Ω 30 100 10k AV = 2 RL = 10Ω –3dB BANDWIDTH (MHz) –3dB BANDWIDTH (MHz) 80 PEAKING ≤ 1dB PEAKING ≤ 5dB –3dB BANDWIDTH (MHz) PEAKING ≤ 1dB PEAKING ≤ 5dB 90 FEEDBACK RESISTANCE (Ω) 100 0 Bandwidth and Feedback Resistance vs Capacitive Load for Peaking ≤ 1dB Bandwidth vs Supply Voltage RL = 30Ω 11 13 9 SUPPLY VOLTAGE (±V) 15 1210 G08 –in 10 en +in 1 10 100 1k 10k FREQUENCY (Hz) 100k 1210 G09 Rev C For more information www.analog.com LT1210 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Supply Voltage 40 RSD = 0Ω 38 TA = 85°C 34 32 30 28 TA = 125°C TA = –40°C 26 RSD = 0Ω 25 15 RSD = 15kΩ 10 5 22 4 16 12 14 8 10 SUPPLY VOLTAGE (±V) 6 0 –50 18 50 25 0 75 TEMPERATURE (°C) –25 100 25 20 15 10 –1.5 –2.0 2.0 1.5 1.0 V– –50 500 0 25 50 75 TEMPERATURE (°C) –25 100 RL = 10Ω –2 –3 –4 RL = 10Ω 4 3 2 RL = 2kΩ 1 V– –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 SOURCING 2.6 SINKING 2.4 2.2 2.0 1.8 1.6 –50 –25 125 50 25 75 0 TEMPERATURE (°C) 60 NEGATIVE 50 125 Supply Current vs Large-Signal Output Frequency (No Load) 100 RL = 50Ω VS = ±15V RF = RG = 1kΩ POSITIVE 40 30 20 10 0 10k 100 1210 G15 90 SUPPLY CURRENT (mA) 70 RL = 2kΩ 125 100 2.8 Power Supply Rejection Ratio vs Frequency POWER SUPPLY REJECTION (dB) OUTPUT SATURATION VOLTAGE (V) –1 50 25 0 75 TEMPERATURE (°C) 1210 G14 Output Saturation Voltage vs Junction Temperature VS = ±15V –25 3.0 1210 G13 V+ AV = 1 RL = ∞ Output Short-Circuit Current vs Junction Temperature 0.5 100 300 400 200 SHUTDOWN PIN CURRENT (µA) RSD = 82.5kΩ 10 Input Common Mode Limit vs Junction Temperature –1.0 5 0 15 1210 G12 OUTPUT SHORT-CIRCUIT CURRENT (A) 30 20 0 –50 125 –0.5 COMMON MODE RANGE (V) SUPPLY CURRENT (mA) V+ VS = ±15V 35 RSD = 47.5kΩ 25 1210 G11 Supply Current vs Shutdown Pin Current 40 RSD = 0Ω 30 5 1210 G10 0 35 RSD = 7.5kΩ 20 24 20 40 AV = 1 RL = ∞ 30 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 35 TA = 25°C 36 Supply Current vs Ambient Temperature, VS = ±15V SUPPLY CURRENT (mA) 40 Supply Current vs Ambient Temperature, VS = ± 5V 80 AV = 2 RL = ∞ VS = ±15V VOUT = 20VP-P 70 60 50 40 30 100k 1M 10M FREQUENCY (Hz) 100M 1210 G17 1210 G16 20 10k 100k 1M FREQUENCY (Hz) 10M 1210 G18 Rev C For more information www.analog.com 7 LT1210 TYPICAL PERFORMANCE CHARACTERISTICS Output Impedance in Shutdown vs Frequency Output Impedance vs Frequency 10k 10 RSD = 82.5kΩ RSD = 0Ω 1 0.1 0.01 100k 10M 1M FREQUENCY (Hz) 100M 18 LARGE-SIGNAL VOLTAGE GAIN (dB) VS = ±15V IO = 0mA OUTPUT IMPEDANCE (Ω) OUTPUT IMPEDANCE (Ω) 100 Large-Signal Voltage Gain vs Frequency 1k 100 10 1 100k 10M 1M FREQUENCY (Hz) VS = ±15V RL = 10Ω RF = 680Ω RG = 220Ω 3RD ORDER INTERCEPT (dBm) 52 9 6 3 0 103 104 105 106 FREQUENCY (Hz) 107 108 1210 G21 + LT1210 PO – 50 680Ω 48 46 220Ω 10Ω MEASURE INTERCEPT AT PO 44 1210 TC01 42 40 12 Test Circuit for 3rd Order Intercept 3rd Order Intercept vs Frequency 54 AV = 4, RL = 10Ω RF = 680Ω, RG = 220Ω VS = ±15V, VIN = 5VP-P 1210 G20 1210 G19 56 100M 15 0 2 4 6 FREQUENCY (MHz) 8 10 1210 G22 8 Rev C For more information www.analog.com LT1210 APPLICATIONS INFORMATION 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 less than 1dB of peaking 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 1dB of peaking and a dashed line when the response has 1dB to 5dB of peaking. The curves stop where the response has more than 5dB of peaking. 14 VS = ±15V CL = 200pF 12 10 VOLTAGE GAIN (dB) The LT1210 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. 8 RF = 3.4kΩ NO COMPENSATION RF = 1.5kΩ COMPENSATION 6 4 2 0 –2 RF = 3.4kΩ COMPENSATION –4 –6 1 10 FREQUENCY (MHz) 100 1210 F01 Figure 1. Also shown is the –3dB bandwidth with the suggested feedback resistor vs the load capacitance. For resistive loads, the COMP pin should be left open (see Capacitive Loads section). 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 10Ω load, the bandwidth drops from 35MHz to 26MHz when the compensation is connected. Hence, the compensation was made optional. To disconnect the optional compensation, leave the COMP pin open. Capacitive Loads Shutdown/Current Set The LT1210 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 6dB 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 greatly reduces the peaking. A lower value feedback resistor can now be used, resulting in a response which is flat to ± 1dB to 40MHz. The network has the greatest effect for CL in the range of 0pF to 1000pF. The graphs of Bandwidth and Feedback Resistance vs Capacitive Load can be used to select the appropriate value of feedback resistor. The values shown are for 1dB 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. 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 LT1210 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 70pF capacitor and the supply current is typically less than 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 74C906 buffer to interface between 5V logic and the LT1210. The switching time between the active and shutdown states is about 1µs. A 24kΩ pull-up For more information www.analog.com Rev C 9 LT1210 APPLICATIONS INFORMATION 15V VIN + VOUT LT1210 – SD quiescent current can be reduced to 9mA in the inverting configuration without much change in response. In noninverting mode, however, the slew rate is reduced as the quiescent current is reduced. RF –15V 5V 74C906 ENABLE 24kΩ 15V RG 1210 F02 Figure 2. Shutdown Interface resistor speeds up the turn-off time and ensures that the LT1210 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. RF = 750Ω RL = 10Ω IQ = 9mA, 18mA, 36mA VS = ±15V 1210 F04a (a) AV = –1 VOUT RF = 750Ω RL = 10Ω ENABLE IQ = 9mA, 18mA, 36mA VS = ±15V 1210 F04b (b) AV = 2 AV = 1 RF = 825Ω RL = 50Ω RPULL-UP = 24k VIN = 1VP-P VS = ±15V Slew Rate Figure 3. Shutdown Operation 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 65 times the current in the Shutdown pin. The voltage across the resistor in this condition is V + – 3VBE. For example, a 82kΩ resistor will set the quiescent supply current to 9mA with VS = ±15V. The photos in Figure 4 show the effect of reducing the quiescent supply current on the large-signal response. The 10 Figure 4. Large-Signal Response vs IQ 1210 F03 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 Rev C For more information www.analog.com LT1210 APPLICATIONS INFORMATION the bandwidth is reduced. The photos in Figure 5 show the large-signal response of the LT1210 for various gain configurations. The slew rate varies from 770V/µs for a gain of 1, to 1100V/µs for a gain of – 1. RF = 825Ω RL = 10Ω VS = ±15V When the LT1210 is used to drive capacitive loads, the available output current can limit the overall slew rate. In the fastest configuration, the LT1210 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 150V/µs, determined by the current limit of 1.5A. 1210 F05a (a) AV = 1 RF = RG = 3kΩ RL = ∞ VS = ±15V 1210 F06 Figure 6. Large-Signal Response, CL = 10,000pF Differential Input Signal Swing RF = RG = 750Ω RL = 10Ω VS = ±15V 1210 F05b (b) AV = –1 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 shut down. Capacitance on the Inverting Input RF = RG = 750Ω RL = 10Ω VS = ±15V 1210 F05c (c) AV = 2 Figure 5. Large-Signal Response 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. Rev C For more information www.analog.com 11 LT1210 APPLICATIONS INFORMATION Power Supplies The LT1210 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. Power Supply Bypassing To obtain the maximum output and the minimum distortion from the LT1210, the power supply rails should be well bypassed. For example, with the output stage pouring 1A current peaks into the load, a 1Ω power supply impedance will cause a droop of 1V, reducing the available output swing by that amount. Surface mount tantalum and ceramic capacitors make excellent low ESR bypass elements when placed close to the chip. For frequencies above 100kHz, use 1µF and 100nF ceramic capacitors. If significant power must be delivered below 100kHz, capacitive reactance becomes the limiting factor. Larger ceramic or tantalum capacitors, such as 4.7µF, are recommended in place of the 1µF unit mentioned above. Inadequate bypassing is evidenced by reduced output swing and “distorted” clipping effects when the output is driven to the rails. If this is observed, check the supply pins of the device for ripple directly related to the output waveform. Significant supply modulation indicates poor bypassing. Table 1 and Table 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 2 oz 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) 2500 sq. mm 2500 sq. mm 2500 sq. mm 25°C/W 1000 sq. mm 2500 sq. mm 2500 sq. mm 27°C/W 125 sq. mm 35°C/W 2500 sq. mm 2500 sq. mm *Tab of device attached to topside copper Thermal Considerations The LT1210 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. 12 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 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. Table 2. Fused 16-Lead SO Package COPPER AREA TOPSIDE* BACKSIDE THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 5000 sq. mm 40°C/W 1000 sq. mm 2500 sq. mm 3500 sq. mm 46°C/W 600 sq. mm 2500 sq. mm 3100 sq. mm 48°C/W 180 sq. mm 2500 sq. mm 2680 sq. mm 49°C/W 180 sq. mm 1000 sq. mm 1180 sq. mm 56°C/W 180 sq. mm 600 sq. mm 780 sq. mm 58°C/W 180 sq. mm 300 sq. mm 480 sq. mm 59°C/W 180 sq. mm 100 sq. mm 280 sq. mm 60°C/W 180 sq. mm 0 sq. mm 180 sq. mm 61°C/W Rev C For more information www.analog.com LT1210 APPLICATIONS INFORMATION T7 Package, 7-Lead TO-220 Thermal Resistance (Junction-to-Case) = 5°C/W 5V 76mA A Calculating Junction Temperature The junction temperature can be calculated from the equation: + TJ = (PD)(θJA) + TA – LT1210 2V 0V –2V VO SD 10Ω VO = 1.4VRMS 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 SO and R packages assuming a 70°C ambient temperature. 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 = (76mA)(10V) – (1.4V)2/ 10 = 0.56W 220Ω –5V 680Ω 1210 F07 Figure 7. then: TJ = (0.56W)(46°C/W) + 70°C = 96°C for the SO package with 1000 sq. mm topside heat sinking TJ = (0.56W)(27°C/W) + 70°C = 85°C for the R package with 1000 sq. mm topside heat sinking Since the maximum junction temperature is 150°C, both packages are clearly acceptable. Rev C For more information www.analog.com 13 LT1210 TYPICAL APPLICATIONS Precision × 10 High Current Amplifier CMOS Logic to Shutdown Interface 15V VIN + + + LT1097 LT1210 COMP – SD – LT1210 SD OUT – 0.01µF 500pF 5V 3kΩ 330Ω –15V 10kΩ 2N3904 9.09kΩ OUTPUT OFFSET:
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LT1210CT7#PBF
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