AAD8092 op amp problem

冰魄3009

AAD8092 op amp problem [Copy link]

maychang

The output terminal of the operational amplifier U27A is marked with U35-5, which is only connected in series with C92C87R90R91. Inputting the signal from this point has almost no effect on the entire circuit.

冰魄3009

maychang posted on 2018-7-12 17:22 The label U35-5 is the output end of the operational amplifier U27A, which is only connected in series with C92C87R90R91. Inputting the signal from this point has almost no effect on the entire circuit.

Hello, Mr. Maychang. U30-1 here is the virtual foundation of the rail splitter TLE2426C. I have always guessed that this amplifier circuit is mainly used to amplify 2MHZ sinusoidal signals. I measured a 100mv 2MHZ sinusoidal signal from U35-5 with an oscilloscope, but this circuit is a bit strange. As Mr. Maychang said, the signal can be directly output from the output terminal, and the operational amplifier does not amplify the signal. If it is to amplify the DC signal, it seems wrong, because C98 cuts off the DC channel. Mr. Maychang, based on your experience, what role do you think this amplifier circuit may play? Or the purpose of this circuit may not be to amplify the signal, etc. I hope you can give me some suggestions? (A17 is the only output terminal of the final stage of the operational amplifier, that is, the sampling port of the ADC of the microcontroller; U35-5 is the only signal input terminal)   

maychang

Bingpo3009 posted on 2018-7-13 09:23 Hello, Mr. Maychang, the U30-1 here is the virtual foundation of the rail splitter TLE2426C. I have always guessed that this amplifier circuit is mainly used to amplify 2M...

I really can't see what the purpose of this circuit is. U30-1 is a 2.5V reference voltage, which is connected to the four op amps' in-phase input terminals to provide bias, that's for sure. The four op amp output terminals are interconnected through a relatively complex RC network, but the signal input terminals of each op amp cannot be found in the figure, which is very strange. U35-5 is unlikely to be the signal input terminal because the capacitance of C91 and C114 to 2MHz signals is only 1.85 ohms. If the signal is input from U35-1, it will be short-circuited to the ground (2.5V reference) by C91 and C114.

maychang

Bingpo3009 posted on 2018-7-13 09:23 Hello Mr. Maychang, the U30-1 here is the virtual foundation of the rail beam splitter TLE2426C. I have always guessed that this amplifier circuit is mainly used to amplify 2M...

"Or the purpose of this circuit may not be to amplify signals, etc." This is possible. But its purpose is not clear.

冰魄3009

maychang posted on 2018-7-13 10:41 "Or the purpose of this circuit may not be to amplify the signal, etc." It is possible. But its purpose is not clear.

Thank you, Mr. Maychang. U35-5 is the output signal of the mixer chip, which is also the only signal input terminal of the op amp. The circuit is also correct. I have always guessed that the MCU samples the A17 signal at the end. I have tried to give A17 DC signals and sine signals, but no data was sampled (there is a sine signal that is smaller than the input signal. The board was burned by water, so I am not sure whether this signal is correct). So from this circuit, in terms of signal amplification, it makes sense that Maychang suspects that U35-5 is not like the signal input terminal, because it is meaningless to amplify the signal. But this is indeed the only signal. Maychang, is it possible that the MCU samples the A17 frequency at the end of this circuit, or the speed of sampling each point of the signal?

maychang

冰魂3009 posted on 2018-7-13 14:18 Thank you, Mr. Maychang. U35-5 is the output signal of the mixer chip, which is also the only signal input terminal of the op amp. The circuit is also correct. I have always guessed...

"Is it possible that the microcontroller in this circuit samples the A17 frequency, or the speed of each point of the sampling signal?" I really can't tell. Please ask someone with high knowledge.