High-accuracy Operational Amplifier Ideal for Current Sensors
We introduce here principle of zero-drift amplifier.
Please check “What is an Operational Amplifier?” too, which explains the general usage and basic terms of an operational amplifier.
1. What is a Zero Drift Amplifier?
While an input offset voltage of 0V is ideal for an operational amplifier, the characteristic dispersion of the transistors that are used in building an operational amplifier generate an input offset voltage. Also, the input offset voltage changes with ambient temperature or elapsed time. It is these changes that are referred to as input offset voltage drift.
A zero drift amplifier is an operational amplifier that minimizes input offset voltage and input offset voltage drift (≒0).Selecting a zero-drift operational amplifier is a highly effective solution for applications that demand high-accuracy signal amplification.
Zero-drift amplifiers contain circuitry that automatically corrects offset voltage. This circuitry is categorized as one of the following three types:
- Auto zero amplifier
- Chopper amplifier
- Combined auto-zero and chopper amplifier
[Auto-zero amplifier]
In addition to a regular operational amplifier (the main amp), an auto-zero amplifier comprises a correction amplifier, capacitors and switches for changing signal paths.The role of the correction amplifier is to measure the input offset voltage of the main amplifier. Measurement data is stored in a capacitor and is used to eliminate the input offset voltage of the main amplifier.This process virtually eliminates input offset voltage.
[Chopper amplifier]
The operating principle of a chopper amplifier is a little more complex. The input signal is converted to an AC signal in an input modulation circuit that comprises a switch. The converted signal is amplified in the amplifier and converted back to a DC signal in an output modulation circuit. Since the input offset voltage does not go through the input modulation circuit, it is converted to an AC signal in the output demodulation circuit. As a result, only the input offset voltage data converted to an AC signal is removed in the low pass filter in the output unit. This process minimizes the input offset voltage.
ABLIC’s Zero-drift Amplifier
ABLIC provides the S-89630A and the S-89713 Series zero-drift operational amplifiers for general use. We also offer the S-19630A and the S-19611A zero drift amplifiers for automotive use.
The S-89630A (for general use) and the S-19630A (for automotive use) operational amplifier realize zero drift operation by auto-zero and chopper architecture. They provide not only low offset voltage attributes, but also wide voltage range (4.0 - 36V) operation.
The S-89713 Series (for general use) and the S-19611A (for automotive use) operational amplifier realize zero-drift operation by auto-zero architecture. They provide low-voltage operation from 2.65V and low offset voltage attributes. The S-89713 Series (for general use) is also available in an ultra small package (SNT-8A: 1.97 x 2.46mm size).
If you are looking for a zero drift amplifier, please refer ABLIC's operational amplifiers. You can check lineup of our operational amplifier in the link "Selection Table" below.