Benz901123
New Member
Hi guys,
Please help me in this. I am designing a voltage controlled current output circuit. It has an input from 0 to 2.5V and it should give current outputs between 0 - 20mA. I was able to do that with a circuit that looks like:
https://www.flickr.com/photos/41126610@N06/5835196217/in/photostream
However, I realise what I actually need is something that looks like:
https://www.flickr.com/photos/41126610@N06/5835730028/in/photostream
where the transistor is sinking the output current into R3(Output Load) instead of sourcing from it.
Circuit number 2 however, doesn't work when I tried modeling it with Pspice. It's been giving me such a headache.
Can anybody help me on whether there're any obvious mistakes I've made in the circuit? Also, some explanations why it doesn't work and some suggestions for a better voltage controlled current source circuit would be extremely appreciated.
Thanks. It's my first post on any forums about problems I've had while working with circuits as I really don't like asking questions unless I'm really really desperate for an answer ( like now).
Cheers,
Benjamin
Please help me in this. I am designing a voltage controlled current output circuit. It has an input from 0 to 2.5V and it should give current outputs between 0 - 20mA. I was able to do that with a circuit that looks like:
https://www.flickr.com/photos/41126610@N06/5835196217/in/photostream
However, I realise what I actually need is something that looks like:
https://www.flickr.com/photos/41126610@N06/5835730028/in/photostream
where the transistor is sinking the output current into R3(Output Load) instead of sourcing from it.
Circuit number 2 however, doesn't work when I tried modeling it with Pspice. It's been giving me such a headache.
Can anybody help me on whether there're any obvious mistakes I've made in the circuit? Also, some explanations why it doesn't work and some suggestions for a better voltage controlled current source circuit would be extremely appreciated.
Thanks. It's my first post on any forums about problems I've had while working with circuits as I really don't like asking questions unless I'm really really desperate for an answer ( like now).
Cheers,
Benjamin