8 bits DAC

137

07:34:57

How can I remove this noise?
It come from the output node of the transistor, the only solution that I've found is to put 1mF on it but because of it, the circuit can't go at medium frequency: when the value of the counter switch from the highest (255) to the lowest (0) I want that the output fall at his lowest value before the counter pass to the next number (1)

published 9 years ago

wyoelk

9 years ago

Put the cap in series with the resistor

deadall127

9 years ago

This doesn't work for the last cap is series with its resistor, I think I don't understand --'

wyoelk

9 years ago

The 1nf cap and 10k resistor at end of circuit are parallel try placing the 1nf cap between the opamp and 10k resistor should help

deadall127

9 years ago

-15V every time

wyoelk

9 years ago

I searched for DAC and everyone is doing it differently. But you may find ond with a solution. Wish I was more help. Maybe post a link to yours on one of their circuits to see if they can help. Did you try increasing the capacitor and/or resistor

deadall127

9 years ago

In fact the resistor is a part of the analogic adder and the cap is to filter very high frequencies, and its value is very close to the limit, a little more and it can't output 20kHz (if it does yet). Also, I posted a 4 bits version and there isn't this problem. But thank you all for the answers :3

2ctiby

9 years ago

Does it help if you drop the impulse period down from its 25 µs to 1 µs

deadall127

9 years ago

Not so much but thanks for the answer;)

2ctiby

9 years ago

Try snipping the wire between the top op-amp and the 10k resistor which is just below it, then put a 100mH inductor there.....that seems to smooth the noise without adverse effects to frequency etc.

deadall127

9 years ago

Yeaaah, seems good, thank you^^

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