LM6172 Voltage Feedback Amplifier: Pinout, Application and Datasheet

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The LM6172 is a dual high speed voltage feedback amplifier. It is unity-gain stable and provides excellent DC and AC performance. With 100MHz unity-gain bandwidth, 3000V/μs slew rate and 50mA of output current per channel, the LM6172 offers high performance in dual amplifiers; yet it only consumes 2.3mA of supply current each channel.

The LM6172 operates on ±15V power supply for systems requiring large voltage swings, such as ADSL, scanners and ultrasound equipment. It is also specified at ±5V power supply for low voltage applications such as portable video systems. The LM6172 is built with TI's advanced VIP III (Vertically Integrated PNP) complementary bipolar process. 

This article provides you with a basic overview of the LM6172 Voltage Feedback Amplifier, including its pin descriptions, features and specifications, etc., to help you quickly understand what LM6172 is.

● (Typical Unless Otherwise Noted)

● Easy to Use Voltage Feedback Topology

● High Slew Rate 3000V/μs

● Wide Unity-Gain Bandwidth 100MHz

● Low Supply Current 2.3mA/Channel

● High Output Current 50mA/channel

● Specified for ±15V and ±5V Operation

The LM6172 is a dual high-speed, low power, voltage feedback amplifier. It is unity-gain stable and offers outstanding performance with only 2.3mA of supply current per channel. The combination of 100MHz unity-gain bandwidth, 3000V/μs slew rate, 50mA per channel output current and other attractive features makes it easy to implement the LM6172 in various applications. Quiescent power of the LM6172 is 138mW operating at ±15V supply and 46mW at ±5V supply.

The slew rate of LM6172 is determined by the current available to charge and discharge an internal high impedance node capacitor. This current is the differential input voltage divided by the total degeneration resistor R_E. Therefore, the slew rate is proportional to the input voltage level, and the higher slew rates are achievable in the lower gain configurations. When a very fast large signal pulse is applied to the input of an amplifier, some overshoot or undershoot occurs. By placing an external series resistor such as 1kΩ to the input of LM6172, the slew rate is reduced to help lower the overshoot, which reduces settling time.

The LM6172 has a very fast slew rate that causes overshoot and undershoot. To reduce settling time on LM6172, a 1kΩ resistor can be placed in series with the input signal to decrease slew rate. A feedback capacitor can also be used to reduce overshoot and undershoot. This feedback capacitor serves as a zero to increase the stability of the amplifier circuit. A 2pF feedback capacitor is recommended for initial evaluation. When the LM6172 is configured as a buffer, a feedback resistor of 1kΩ must be added in parallel to the feedback capacitor.

Connection Diagram

LM6172 Simplified Schematic (Each Amplifier)

● Scanner I-to-V Converters

● ADSL/HDSL Drivers

● Multimedia Broadcast Systems

● Video Amplifiers

● NTSC, PAL and SECAM Systems

● ADC/DAC Buffers

● Pulse Amplifiers and Peak Detectors

Differential Line Driver

I-to-V Converters

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