IDAC and Trans-Impedance Amplifier

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Anonymous
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 Hi all,

   

PSOC 5 has an IDAC with 8MSPS. In my application, I required sinewave up 160kHz. Can I pass the output of IDAC to an trans-impedance amplifier so that I get sinewave in voltage format?

   

Thanks

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Bob_Marlowe
Level 10
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I do not see any reason why you may not do that.

   

Btw: There is a WaveDAC component availlable that uses the IDAC. Have a look at the Datasheet www.cypress.com/. Will simplify some things.

   

 

   

Bob

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ETRO_SSN583
Level 9
Level 9
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Some considerations -

   

 

   

1) TIA may have be offset to handle fact it is inverting. Or  change

   

polarity of IDAC.

   

 

   

2) TIA conversion R tolerance is 60%, you will have to factor that in

   

to determining amplitude range you will get.

   

 

   

3) You need to calc slew rate needed for 160 Khz and pk-pk range

   

you want. The basic PSOC OpAmp (used in TIA) ranges from .9 to

   

3 V/uS. www.radio-electronics.com/info/circuits/opamp_basics/operational-amplifier-slew-rate.php

   

 

   

4) You have to manage compliance range of IDAC in your calculations.

   

 

   

5) Consider terminating IDAC with a low R like a K or so, then buffering

   

that pin with an OpAmp.

   

 

   

6) At 160 Khz, N samples/period, your table lookup loop has to run at

   

N x 160 Khz, just a consideration.

   

 

   

Regards, Dana.

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Anonymous
Not applicable

 Hi Thanks all for your swift response.

   

Appreciated

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ETRO_SSN583
Level 9
Level 9
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If you want a 1V sine pk-pk at 160 Khz, 32 samples, you will see you can't

   

do it with WaveDAC8 because of settling time of VDAC. In fact you either have

   

to drop Fsamp by ~ 5 or the # samples by ~ 5, translate lots of distortion. And you are

   

right up against the slew rate of the OpAmp in WaveDAC8. In fact if you terminate

   

the IDAC externally with a low Z R (to get fast setltling time) you still have to go thru

   

OpAmp to buffer, or live with terminating R as your output Z for the sine gen.

   

 

   

Do the calculations.

   

 

   

Regards, Dana.

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Anonymous
Not applicable

Hi Dana,

   

Many thanks to your reply.

   

Do you think the following will work.

   

Instead of using the internal components of PSOC 5 to buffer, can I used external components, including resistor and high speed trans-impedance amplifier to perform the current to voltage conversion?

   

Thanks. 

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