Hi team,
The customer is using LM6171BI for the integral circuit application. He uses two LM6171 devices. The input signal is the sine with amp=1Vpp,
f=5KHZ. The power supply is +/12V. He measures the output signals through the oscilloscope. Please check the fig 1. The green waveform is
the input signal. The yellow waveform is the output waveform for U1 which is in my TINA circuit. The blue waveform is the output waveform
for U2 which is in my TINA circuit. From the output waveform, the yellow waveform is the sine and it is fine. But the blue waveform is
not the sine waveform. It is not integrating at all.
Then follow the customer's circuit, I design a TINA circuit. From the output waveform, the output waveform for U1 is fine, it is also the sine.
But the output waveform for U2 is bad, it is not the sine. Please check the fig 2. Then I change the R4 value. When I select 1K,10K or 15K
for R4, the output waveform for U2 can be fine. The fig 3 is the output waveform when R4 is 15K. But when R4 is more than 20K,
the output waveform for U2 will be bad.
Q1: So, I would like to know why I reduce the R4 value, the output waveform for U2 can be fine. My Tina circuit is also in the attach.
Q2: If I change R4 to bellow 15K value, the U2 output waveform will be fine, is this solved the customer's issue?
fig 1
fig 2
fig 3
Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments