Mono audio signal to stereo amplifier IC - Page 1
Forum section: electronics / beginners

author: de_light
author_rank: Regular Contributor
timestamp: April 26, 2022, 02:20:51 am
content: I am trying to amplify an audio signal being output from an Arduino pin. It is mono.The amplifier IC I have is a PAM8302A 2.5W Class-D mono audio amplifierhttps://www.diodes.com/assets/Datasheets/PAM8302A.pdfI am a little confused as to the input to the IC though. It has a IN+ and an IN-. The audio signal is only coming off one pin on the Arduino.Am I expected to tie the IN- (pin 4) to ground?

author: bdunham7
author_rank: Super Contributor
timestamp: April 26, 2022, 03:38:04 am
content: Yes, but don't forget to put input capacitors on both inputs as shown in the typical application schematic.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2022, 09:18:53 pm
content: The datasheet doesn't actually have an application schematic for this situation. It's an amp with a differential input, and the schematic only shows a differential source.To connect a differential-input amp like this to a single-ended output (like the Arduino), you do indeed need a cap to each input, with the IN- going to ground via that cap. (In the app notes for a different amp I am using, which also has differential inputs, it says to put the cap on IN+ close to either the input or source, and the cap on IN- close to the source, to minimize noise).----------|Arduino |-out ---||-------------------------------------------[IN+]|-GND --||-------------------------------------------[IN-]----------|or----------|Arduino |-out ----------------------------------------||------[IN+]|-GND --||-------------------------------------------[IN-]----------|P.S. de_light, maybe change the thread title, since this has absolutely nothing to do with stereo.

author: bdunham7
author_rank: Super Contributor
timestamp: April 27, 2022, 09:38:27 pm
content: Quote from: tooki on April 27, 2022, 09:18:53 pmThe capacitors are needed because the IC self-biases the inputs to VDD/2. The schematic will work (with capacitors) with any source AFAIK.

author: tooki
author_rank: Super Contributor
timestamp: April 28, 2022, 10:41:15 pm
content: Quote from: bdunham7 on April 27, 2022, 09:38:27 pmYyyyeah… I know that, and I didn’t say anything contrary to those statements. What Ididsay is that the datasheet doesn’t show how to connect a single-ended source to its inputs, and so I provided clear explanations of how to do just that.Your reply didn’t tell the OPhowto connect their single-ended source, only to “put input caps on both inputs as shown in the datasheet” — the datasheet that lacks a relevant example. How to connect via caps might be obvious to an experienced engineer, but your reply was of zero help to the OP unfortunately.

author: bdunham7
author_rank: Super Contributor
timestamp: April 28, 2022, 10:59:37 pm
content: Quote from: tooki on April 28, 2022, 10:41:15 pmI'm sorry if it wasn't clear, but....he said:QuoteAnd I replied:QuoteI suppose would bepossibleto not understand that clearly, in which case your pictures would help. But I think most people would understand.

author: tooki
author_rank: Super Contributor
timestamp: April 29, 2022, 05:22:32 am
content: “Tie to ground” means connect directly to ground, which isn’t correct here. Given that this is the beginners forum, I think it’s wiser to be unambiguous about how things need to be wired, that’s all.