I’ve been looking at the theoretical principles that govern the voltage-controlled amplifier (VCA) recently and came across some simple VCA designs that caught my attention. A common technique involves a JFET and an opamp to achieve VCA type operation by using the JFET as a voltage-controlled resistor somewhere in the input path. I’ve seen a…
Tag: bjt
Differential Amplifier w/ Cathode Follower
This is a circuit designed for a classroom project whereby the instructions were to “improve” a differential amplifier circuit. The differential amplifier design is essentially an exercise in understanding the inner workings of an opamp, and it effectively works in the same way. The figure below is a schematic for the differential amplifier without the…
mellotronium 2.0: rebuild
after our move to Oregon two months ago, i’m finally getting back to a spot where i can do more building and experimentation. that being said, my arduino-based sampler/synth is getting a rebuild to make it more capable and road-worthy. the LED segment display is currently showing voltage out what should be 5v DC. i…
MOSFET vs. BJT
a good rule of thumb pulled from this forum thread (http://www.electro-tech-online.com/general-electronics-chat/39339-mosfet-vs-bjt.html): Need a switch to be fully-on fully-off and carry lots of current -MOSFET Need a switch that needs to have lowish capacitance – BIPOLAR Need a cheap, dirty 2 or 3 component current source – BIPOLAR Need a low voltage/noise amplifier – BIPOLAR Need…
PT2399 with BJT preamp
here’s a short clip of the delay circuit that i intend to convert to a stomp box. i’m still working out the kinks in the pre-amp stage to solidify the input signal from the guitar though. just a sample though to hear how it might sound with some guitar tones. more soon.