Hos to trigger this input ?

[ericgibbs]

Thanks for these explanations.

I have an other question regarding the choice of an AOP.
When I read some general book or article found on the web, every thing is simple. But it seams that in the real life think are more complicated.
So how I guy as me with only limitated knowledge in electronic can do to select an AOP without to much error ?

Jean-Marie

hi,
The TLC082 opa looks a good choice.
Ref the series resistor in the output of the final opa stage, as you are driving a PIC's pin input, I would recommend that you use a 470R.
This will limit the PIC's protection diode current should the output of the opa exceed +5V.

As you are counting the 5KHz pulses, ensure that the final stage output swings thru the high/low threshold levels of the PIC input.

If possible select a PIC input pin thats has a schmitt input or else you could use one of the Timer inputs.

 

[schneiderj]

Supply voltage, supply current, input current, inpit common-mode voltage range, max frequency and noise level are all things that you should consider when selecting an opamp.

Ok thanks for these informations.

Jean-Marie

 

[schneiderj]

If possible select a PIC input pin thats has a schmitt input or else you could use one of the Timer inputs.

Normaly I will use TMR0 as counter, so it should be OK.

Thanks
Jean-Marie