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# Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Anonymous
Not applicable

Hello Every one,

I took one example code for PGA. I set 1 V from VDAC and measuring the output. The problem is, if i set gain of 8 or higher it is only showing me 3.284 V on Multimeter.

Can you tell me why this is happening and how i can get rid of this thing?

Regards

Awais

9 Replies

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Anonymous
Not applicable

I am using PSOC 5LP.

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Level 9
Level 9

The input and output V limits of a psoc pin and analog

are basically Vdda >= Vanalog >= 0. So with a G = 8, and

input of 1 V, you are asking for 8V out, which exceeds your

Vdda.

Regards, Dana.

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Anonymous
Not applicable

Sorry,

How i can set my Vdda Value in order to get accurate result?

Regards

Awais

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Level 9
Level 9

The CM range is limited by -

Vdda >= Vanalog >= 0 and Vdda is basically limited to 3.3 V or 5V, see spec sheet

for exact number.

You cannot get > Vdda out of the chip.

Regards, Dana.

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Anonymous
Not applicable

oh yes,

Now i know what do u mean 🙂

Regards

Awais

Level 9
Level 9

Regards, Dana.

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Anonymous
Not applicable

Hi One more time 🙂

So this means it applies to normal op amps also?

I cannot get more than 5 volts?

Am i right?

Regards

Awais

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Level 9
Level 9

Thats correct.

If you need to get higher voltage swings you can use external parts, split power

supplies to do that.

Regards, Dana.

# Re: Why PGC is showing maximum voltage level (3.284 V) even if i am increasing gain?

Level 9
Level 9

If you need to produce higher V swings that a PSOC Vdda allows you

can use external OpAmp running on higher voltages, and / or split supplies.

Some ways of generating simple negative supplies for a split supply application

here -

Note you can, in some applications, use an unregulated supply on external OpAmp

because its PSRR aids in reducing its supply sensitivity to changes in its supply.

Regards, Dana.