[sdiy] Generating +5V gate signals from +3.3V logic

[Tom Wiltshire]

On 4 Mar 2012, at 11:34, Jason Tribbeck wrote:

> On 4 March 2012 11:27, Tom Wiltshire <tom at electricdruid.net> wrote:
> Hi All,
> 
> Subject says it all really.
> 
> I'm running a 3.3V dsPIC and I want to generate 0-5V gate outputs from it. I've got a 3.3V supply for the uP, and a +/-12V for the op-amps, but no +5V supply.
> 
> Is there a simple way to get a 0-5V output without having to add a +5V supply?
> 
> Obviously if I have the +5V supply I could use some logic convertor chip, but I'd like to avoid another supply for one single chip if possible.
> 
> 
> PNP transistor to pull down the +12V line, followed by a resistor to create a potential divider?
> 
> So, the collector's resistor would be, say, 70K, and the emitter's resistor would be, say, 50K. If the transistor is off, then the two would form a 120K total resistance, and the 70K part would mean the output voltage is 5V. With the transistor on, it should be 0V.
> 
> However, this is a bit of guess work; I'm normally dealing with 12V to 5V/3.3V for automotive work, and my synth stuff is all digital :)

Thanks Jason.

Currently I'm thinking that an op-amp is the way to go. Feed a 0-3.3V digital signal in, apply a little gain, get a 0-5V signal out. Run the op-amp on the analog +/-12V rails and consider it as output buffering into the bargain. What do you think?

T.