Here is a bad picture of the output of the AC128 buffer that was described in the previous article. It is a 2v pk-pk, 100kHz triangle wave going through the exact setup shown in the schematic. The response is flat from 10 to 100kHz and beyond – excellent performance. This test was run with the leaky PNP transistor operating on a 9v battery.
I tested 10 leaky AC128s and got identical performance from all of them, with current leakage measured in the range of 400uA to 700uA.
Great Oscope bro! Is that you that I can see in the reflection?!?! That scope reminds me of some of the US Navy stuff that I had to use in repair shops early on. BK Precision makes great test gear. I was surprised by how well those transistors worked being leaky, then got to think, those devices were used all of the time in radio/RF circuits so they HAD to perform to that level as a minimum.
Good work Jack!
Robert
I’ve owned the B&K for more than 25 years and it was not new when I bought it in a pawn shop. It still works great!
-Jack
Hey Jack! Does forward gain (bias) matter on the device? I’ve got a ton of PNP devices and the gain is rather low?
The beta is part of input impedance equation and the higher the hfe, the greater the input Z will be.
regards, Jack