OPA928EVM: Use OPA928 integrator with a sample/hold mode

HAYDAR BILHAN

Prodigy 55 points

Part Number: OPA928EVM
Other Parts Discussed in Thread: OPA928

Tool/software:

We are planning to use OPA928 in integrator mode as shown on Figures 4.4 to 4.6 of the EVM user guide.

How can we implement Sample/Hold? Output will be sampled by an ADC after a fixed integration duration.

3 months ago

0 Raymond Zhang1 3 months ago

TI__Guru* 76461 points

Hi Haydar,

HAYDAR BILHAN said:
How can we implement Sample/Hold? Output will be sampled by an ADC after a fixed integration duration.

Here is the Figure 4.4 to 4.6. What type of sample/hold event do you want to implement? Typically, the sample and hold is implemented after an op amp's buffer, like the image below (high input impedance and charge up the sample and hold capacitor). Some of ADCs also have sample and hold features.

There are other types of sample and hold circuits, such as op amp buffer output + cap, switched-capacitor, and closed-loop sample and hold circuit. It depends on how long is the hold and how accurate you want to hold the samples. In the image above, the ultra low current leakage thin film capacitors are typically used in the sample and hold circuit.

Here is some TI sample/hold IC