Transistor-Based Voltage Controlled Amplifier (VCA)

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This is a continuation of last time, where we learned how a simple differential amplifier (diff amp) works. We're going to take that design and add a clever thing called a current source in the 'tail' of the circuit, and see how that makes the circuit voltage controllable!
This is a more advanced, and much improved VCA compared to my 1 Transistor VCA. We've come a long way!
Schematic: drive.google.com/file/d/1vJ6e...

[@els1f]

These videos are incredible, man thank you 🙌 For YEARS the conventional vs electron flow thing really gets in the way of me intuiting schematics

[@TheAudioPhool]

Curse you Ben Franklin!!

[@duality4y]

I really enjoyed this video i am very curious for what is up next :) your enthusiasm gets me really in the mood to try and build these things myself!

[@MeeBilt]

Beautiful design and a great explanation! 😊

[@davebutler3905]

Just found your channel! You are excellent at breaking things down and explaining each stage. You clearly understand the components with practical familiarity. Unlike professors that model components with formulas... and consequently never actually work. Thanks a million! I'm interested in non linear/logarithmic amplifier circuits... If you have anything like that to share!?

[@ThangPham-wz9ns]

really appreciate your work, you teach me what my lecturer can't. Thanks a lot

[@AndersWeijnitz]

Super cool! Very interesting!

[@Oleksii.M]

I'm trying to make synth at home as a hobby and your videos help a lot. Thanks for your work! Hope to see more content from you in the future.

[@icollided]

Excellent video!

[@pauldery7875]

Great explanation of this circuit, you are a masterfull teacher. Thanks for sharing!

[@achimbuchweisel2736]

nice tutorial :) thanks a lot

[@alfredtambunan8961]

Billion thanks teacher! Now I am ready to built frequency 340 GHz using transistors, due unavaialbe Op Amps in the market!

[@noel101082]

You are absolute gold mate. Might have to switch out those pwm LEDs though.

[@oakspines7171]

May I add something here. In AC analysis, the concept of Virtual GND is introduced as a shortcut to simplify the process of solving the circuit equations. It does not change the final result of the math but makes it much simpler to visualize and do the math. You can leave the RE in there and solve the equations with same result as considering the node a virtual GND. It just makes the math more hairy but would have same result due to the Differential nature of the circuit.

[@fer_fdi]

Excellent!

[@domiloik]

Nice video and very usefull informations. What transistor are you using? Any BOM to build this circuit?

[@sukhithalakwan]

I've came across some schematics each emitter having its own resistor to the negative rail and I want know about them too

[@kamleshchavan7451]

Sir any videos on Radio Control circuit's for example RC toys circuit's how they work , how the signals are transmitted from transmitter to receiver to control the dc motors of the RC toy car

[@t1d100]

More kewlness...

[@plamenpetkov7132]

The simplest current source is the zero biased JFET

[@glowfly]

i would go to school if this was the teacher etc you know the meme

[@mortenrobinson5421]

15:46 no offense, but it sounds nothing like a sine. Sounds like a lot of harmonic overtones are introduced. Looks right on the oscilloscope, but it doesn't sound right.

[@djturbofiwip2137]

could be a poor mic getting overdriven tho

[@woosix7735]

the voltage dividers for +-5V are 400 ohm with 9 volts across them which means about 44mA through each one! almost 90mA just for one VCA! seems kinda wastefull to me