INA128 Instrument Amplifier

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The theoretical amplification factor of INA128 is 100 times when RG=500 ohms. When the input is 150KHz, 10mV AC, its amplification factor remains almost unchanged. Why is it like this?

dwwzl

It is not recommended to use simulation software, it is also good to build a demo board

maychang

"When the input is 150KHz, 10mV AC, the amplification factor remains almost unchanged"

Within the working bandwidth, the amplification factor should remain unchanged.

xiaxingxing

maychang published on 2020-4-20 08:06 "When the input is 150KHz, 10mV AC, the amplification factor is almost unchanged" Within the working bandwidth, the amplification factor should be...

Senior, does he mean that when the frequency of the input signal is 150khz and the amplification factor is 100 times, the gain-bandwidth product exceeds the allowable value.

So when the frequency of the input signal is 150khz, the amplification factor is less than 100 times. Is this the correct understanding? ? ?

maychang

xiaxingxing posted on 2020-4-20 11:43 Senior, is this what he meant? When the frequency of the input signal is 150khz and the amplification factor is 100 times, the gain bandwidth product exceeds the allowable value. So...

I don't know either.

However, the op amp specification states that the -3dB bandwidth is 200kHz when the gain is 100 times. It should drop by less than 3dB when the input signal is 150kHz.

chunyang

I don't think the original poster is asking about gain-bandwidth, so the description is probably wrong. Judging from the original poster's description, it is normal for the gain to remain almost unchanged in the simulation software, after all, it is within the device's parameter range. In the actual circuit, it should be possible to observe a decrease in gain.