Guru
Joined: 11/02/2018
Location: AustraliaPosts: 2447
| Posted: 11:53pm 28 Nov 2022 |
The average voltage on the Pico pin should be about 1.65V and the frequency 44.1kHz even with no modulation. If you can get that measure V and f on the base and collector.
I would expect the average readings to be 0.3V B-E and 2.5V C-E with 44.1kHz on both.
"Edit: I'm guessing it is something to do with the phrase in the manual "... relies
on capacitor coupling into the following amplifier ...""
That is for a "proper" linear audio amplifier.
This simple circuit is a "Class D" digital amplifier and relies on the DC component in the Pico output to forward bias the B-E junction. A capacitor would block that and require additional components.
Edited 2022-11-29 10:07 by phil99