OP07: Calculation of output impedance of operational amplifiers in practical use

SHENG YANG

Part Number: OP07
Other Parts Discussed in Thread: TINA-TI

Hi, TI engineer!

As shown in the above figure.Input is battery voltage.OP07 operational amplifier differential.Input to DSP ADC pin.How to calculate the output impedance of the operational amplifier in the red mark position of the picture(It is also the input impedance of ADC.)Please help me.Thank you very much.

over 6 years ago

0 Clemens Ladisch over 6 years ago

Guru 317370 points

Due to the RC filters, the output impedance depends on the frequency.

As shown in figure 3 of the TMS320x2802x, 2803x Piccolo Analog-to-Digital Converter (ADC) and Comparator Reference Guide (SPRUGE5), the ADC's sample-and-hold circuit has a capacitance of a few pF. This means that the 47 nF capacitor is more than enough to buffer the voltage.

0 Tim Green1 over 6 years ago in reply to Clemens Ladisch

TI__Expert 6275 points

Two Things that will help answer this. You can accurately model the input of the ADC and simulate the op amp driving the ADC to see performance before you ever build a PCB.

See collateral the following link:

And consider downloading and using the free SPICE simulator TINA-TI:

0 Dennis Goeke over 6 years ago in reply to Tim Green1

TI__Genius 11135 points

Jin

We haven't heard back from you so we assume this resolved your issue. If you need more help just post another reply below.

Thanks
Dennis

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OP07: Calculation of output impedance of operational amplifiers in practical use