NS LMP8100A可编增益放大器应用方案

NS LMP8100A可编增益放大器利用软件调节增益，增益则由1V/V至16V/V，共分为16个步级, 以1V/V作为一步级增减, 在摄氏-40度至 125度的工业温度范围内操作, 增益准确度保证可达0.03%,而在摄氏-40度至 85度的温度范围内操作，增益准确度保证可达0.075%。LMP8100!可编程增益放大器的核心，具有33MHz CMOS 输入、轨到轨输入/输出（RRIO）运算放大器、典型的110dB开环增益等特征,非常适用于工业设备及测量仪表等产品.本文提供了LMP8100的主要特性,方框图以及测试电路和应用电路图.

此外，美国国家半导体也推出型号为LMP8100的半高精度级别可编程增益放大器，其特点是只要在摄氏-40度至 85度的温度范围内操作，增益准确度保证可达0.075%。这两款放大器的闭环增益可以通过一列共16个高精度薄膜电阻加以设定。这两款可编程增益放大器的核心，都具有33MHz CMOS 输入、轨到轨输入/输出（RRIO）运算放大器、典型的110dB开环增益等特征、。适用于工业设备及测量仪表等产品
LMP8100A芯片可提供四种级别的内部频率补偿，因此即使采用较高的增益比率，可供使用的信号带宽也会随着增加。这款芯片设有输入零校准功能，可让用户测量输出偏移电压，以便校准因温度或电压漂移而产生的任何误差。此外，这款放大器的控制模式可以通过串行端口加以设定，甚至几颗芯片也可以通过这一串行端口串联一起，这样一列多颗LMP8100放大器可以利用微控制器的串行数据流加以设定。这款芯片的控制模式寄存器采用两个缓冲区，确保不同设定之间的变换不会出现信号跳变。

LMP8100A芯片的压摆率为12V/us，而单位增益带宽为33MHz。这款芯片适用于2.7V至5.5V之间的供电电压，若供电电流为5.3mA，可以输出20mA的电流。如果采用停机模式，耗电量可降低至20uA。

LMP8100A及LMP8100两款芯片都采用美国国家半导体专有的VIP50 BiCMOS 放大器系列的最新型号产品。这系列放大器可以大幅提高系统的精度，并降低功耗。工艺技术制造，是该公司的高精度、低电压及低功率LMP



LMP8100 Programmable Gain Amplifier

概述:

The LMP8100 programmable gain amplifier features an adjustable gain from 1 to 16 V/V in 1 V/V increments. At the core of the LMP8100 is a precision, 33 MHz, CMOS input, rail-torail input/output operational amplifier with a typical open-loop gain of 110 dB. Amplifier closed-loop gain is set by an array of precision thin-film resistors. Amplifier control modes are programmed via a serial port that allows devices to be cascaded so that an array of LMP8100 amplifiers can be programmed by a single serial data stream. The control mode registers are double buffered to insure glitch-free transitions between programmed settings. The LMP8100 is part of the LMP  precision amplifier family and is ideal for a variety of applications.

The amplifier features several programmable controls including: gain; a power-conserving shutdown mode which can reduce current consumption to only 20 μA; an input zeroing switch which allows the output offset voltage to be measured to facilitate system calibration; and four levels of internal frequency compensation which can be set to maximize bandwidth at the different gain settings.

The LMP8100 comes in a 14-Pin SOIC package.

特性:
Typical Values, TA = 25°C
■ Gain error (over temperature range)
— LMP8100A 0.03%
— LMP8100 0.075%
■ Gain range 1 to 16 V/V in 1 V/V steps
■ Programmable frequency compensation
■ Input zero calibration switch
■ Input offset voltage (max, LMP8100A) 250 μV
■ Input bias current 0.1 pA
■ Input noise voltage 12 nV/√Hz
■ Unity gain bandwidth 33 MHz
■ Slew rate 12 V/μs
■ Output current 20 mA
■ Supply voltage range 2.7V to 5.5V
■ Supply current 5.3 mA
■ Rail-to-Rail output swing V+ −50 mV to V− +50 mV

应用:
■ Industrial instrumentation
■ Data acquisition systems
■ Test equipment
■ Scaling amplifier
■ Gain control
■ Sensor interface


图1.器件方框图.



图2.器件测试电路图.



图3.桥放大器电路图



图4.LMP8100应用电路图.