Simple DAC Output Amplifier Circuit? - Page 1
Forum section: electronics / projects

author: hal9001
author_rank: Regular Contributor
timestamp: September 08, 2021, 10:52:48 am
content: I want to amplify the output of a single supply DAC to handle higher currents up to 500 ma. The frequency will range between 100 hz to 10 Mhz. What's a simple circuit to do this?I found this example but I dont know how well it will work.Cheers!

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 08, 2021, 11:07:44 am
content: I guess, more information are needed to help youIf you say you'd like to control currents by a DAC, it sounds like you want an adjustable current source/sink;then you talk about frequencies upto 10MHz what make me think of an RF amp, what is a complete different subject which normally doesn't need any DACp.s.ok, now you added a pic while I wrote; that shows a current sink, which can be controlled by a DAC, but it's still not clear what you want with RF; a current source can be toggled on/off but not upto 10MHz; that serves no useful purpose; normally you use a few kHz

author: hal9001
author_rank: Regular Contributor
timestamp: September 08, 2021, 11:27:13 am
content: Quote from: HB9EVI on September 08, 2021, 11:07:44 amThanks. I should clear up that I want to make a sine wave generator for a project. Sorry if I describe this badly as analog circuits are new for me.I want to build an amplifier circuit that if I apply a load to the output of the DAC, then the output signal doesnt collapse for source currents up to 500 ma.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 08, 2021, 11:45:47 am
content: what you describe, are two different things:one is a current sink/source, which is entirely for a DC current, not for AC; the approach for a DAC adjustable current source simply doesn't works with AC signalsthe other thing is an amp for RF, where you normally don't work with voltages or currents but with impedances, an RF amp is designed to drive a specified nominal impedance, which is normally 50 ohmsyou are mixing two different worlds together in a way which is not working like that

author: magic
author_rank: Super Contributor
timestamp: September 08, 2021, 11:54:40 am
content: OP wants a unity gain buffer with 10MHz bandwidth and 0.5A peak output driveThe class A emitter follower most likely won't cut the mustard because sinking current is limited by the resistor (and voltage across the resistor, aka the momentary output voltage).

author: Cerebus
author_rank: Super Contributor
timestamp: September 08, 2021, 12:55:18 pm
content: Quote from: HB9EVI on September 08, 2021, 11:45:47 amReally?Quick, someone tell Analog that LTSpice is broken! It allows AC currents on a circuit that is "entirely for DC current".

author: Cerebus
author_rank: Super Contributor
timestamp: September 08, 2021, 12:59:34 pm
content: Quote from: hal9001 on September 08, 2021, 10:52:48 amThis looks like a classicXY problem. (Read the link if you haven't heard the term before.)What are youactuallytrying to do in the first instance? Not in the"amplify something"sense but in the"I'm trying to connect a DAC to XXX to do YYY".

author: voltsandjolts
author_rank: Unknown
timestamp: September 08, 2021, 01:04:20 pm
content: https://www.eevblog.com/forum/testgear/juntek-dpa-2698-10mhz-signal-amplifier-digilent-analog-discovery/msg3649978/#msg3649978

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 08, 2021, 01:18:23 pm
content: Take a look at DSL and PLC line driver chips.