OP07C: About the size of feedback capacitor in differential operational amplifier circuit

SHENG YANG

Part Number: OP07C
Other Parts Discussed in Thread: TINA-TI, LMC6482

Hello, TI engineer!

As shown in the figure above, how do I get the value of the red loop capacitor C2/C4 in the circuit, and I want to get detailed information. Thank you!

over 6 years ago

0 Tim Green1 over 6 years ago

TI__Expert 6275 points

Closed loop BW is set by C2 with a pole at fp=1/(2*pi*R2*C2).

Non-inverting input filter is set by C4 with a pole at fp = 1/(2*pi * C4*R3//R4) where R3//R4 = (R1*R2)/(R1+R2).

In addition consider downloading the free SPICE simulator from TI, TINA-TI at:

http://www.ti.com/tool/tina-ti

By building and simulating your circuit in TINA-TI many problems can be avoided before building it in the real world. If you have problems once the circuit is built in TINA-TI feel free to post the schematic from TINA-TI on the E2E Forum for further assistance.

0 SHENG YANG over 6 years ago in reply to Tim Green1

Expert 1230 points

Thank！Tim Green1！

0 kai klaas69 over 6 years ago

Guru 140200 points

Hi Jin,

to get the best common mode rejection at DC and AC, the components R1...R4, C2 and C4 should be matched, like shown is section 8.1.3 of datasheet LMC6482. e.g.

Kai

0 SHENG YANG over 6 years ago in reply to kai klaas69

Expert 1230 points

Thank！kai !

0 SHENG YANG over 6 years ago in reply to kai klaas69

Expert 1230 points

Hi ! kai !
Please look at the following link. Thank you!
e2e.ti.com/.../743977

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OP07C: About the size of feedback capacitor in differential operational amplifier circuit