Ugly Circuit Boards - for experienced electronics makers: Video posted Jan 12, 2025

Video posted Jan 12, 2025 :: https://youtu.be/-is1NowfrtA

Resources for 'Ugly Circuit Boards::

 

Above — Schematic of the so simple AF presented in the video.

Above — The so simple PA stage in a test bench setup: 1KHz signal generator, 8 Ω dummy load and DSO.

Above — Clean output FFT of the so simple PA when driven to 288 mW signal power across the dummy load.
 

Above — 2 users requested a higher power version with (hopefully) the same parts count. I employed 2  packaged Darlington emitter  followers -- the TIP122 / TIP127 pair instead of the 2N4401 / 2N4403 followers.

 

Above — I had to add 2 diodes to the PA bias stack, plus an additional DC filter capacitor  which increased the parts count by 3 items. The 22 Ω DC low-pass filter is now moved on the other side of the NPN transistor to avoid a big voltage drop across that resistor with the higher DC current drive of the 'big guns' PA pair. A 470 µF bypass cap gets added to the DC supply of the TIP122 to low-pass filter the output followers. 

 Above —  Clean output in time domain with the alternate so simple PA  driven to 700 mW signal power across the dummy load.

 
 
Above —  Clean output FFT of the alternate so simple PA when driven to 700 mW signal power across the dummy load.