Bypass cap questions

[szzuk]

I'm making up a board that uses the opa549 operational amplifier, it is high volts and current (60V/10A). The datasheet says it needs low esr bypass capacitors, that are tantalum and ceramic. This is a rough and ready circuit, so do I have to bother with low esr? low esr seems to suggest an expensive surface mount tantalum whereas i can't see the problem with a cheap electrolytic.

 

[Bob Scott]

I viewed the datasheet and did not see a value for power supply rejection. I think your best bet is to give TI a call. Ask to speak to an applications engineer for the OPA549. Tell them about your concerns and questions. It's a free service.

 

[edeca]

Well you don't have to bother, but then you can't expect the device to work within the specifications of the datasheet. That said it stands a good chance of working just fine, you will just have to try it.

Electrolytic capacitors are not well suited for bypassing. The role of the bypass capacitor is to filter out the high frequency noise on the power supply rail, an electrolytic generally can't respond fast enough for this.

This one has bitten me before, I designed a board with a number of different sensors and a radio module. Every so often the radio would simply reset. Adding a large ceramic and a small ceramic across the power rails near to the radio module fixed it. The large ceramic in my example would be the tantalum from your datasheet.