Setting the operating point using Active methods

#169 In this video I continue to look at methods to stabilize the bias point of a transistor amplifier, this time by using active methods. I first look at what can be done on the design and component selection part and then look at some active electronic compensation methods.
Miniseries with related content:
BJT DC operating point: • Setting the operating ...
FET DC operating point: • Setting the operating ...
Active DC operating point: • Setting the operating ...
Further reading and datasheets:
assets.nexperi...
www.ok2kkw.com...
www.qsl.net/va...
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[@RicardoPenders]

Of all the explanations I found online this one is by far the best because you always make it so easy to follow and understand.
I find it very helpful that you show the LTSpice models to get a better idea of what the circuits do when it's active.
Keep up the good work FesZ Electronics.

[@Choober65]

I'm a long time Electronics Engineer and I found this VERY useful.

[@guillermorojas2000]

Your videos are addictives man

[@biswajit681]

Yes need videos more frequently 😜 it's more addictive than Netflix and Amazon prime

[@unsearchablethings8167]

He makes some great videos, with great explanations.

[@gjvdspam]

Yes yes yes, the comparator circuit in 11:00 and than the example circuit finally made a click. (still have a lot to learn hehe) Thank you.

[@DanielSMatthews]

That was very helpful, I understand the topic much better now, thanks.

[@andymouse]

Another great tutorial !....cheers.

[@electroquests]

Thank you for the video. This is very helpful. I loved the part about non-integer number of diodes, that was brilliant.

[@aduedc]

Very good presentation. I learned from this presentation. Thanks

[@BrijeshKumar_electrical]

Happy Teacher's Day Sir

[@nidhinbenny7975]

Nice video as always :)

[@stelian95]

Nice video as always!

[@patrickwright8552]

11:00 & 16:11 The op-amp's inputs should be flipped. The feedback should flow into the op-amp's positive input, since its output signal is sent to an inverting common emitter BJT, and then back to the op-amp. As drawn, the circuits are positive feedback loops. The BJT-based circuits work properly because the BJTs receive Vref at their inverting base terminal and the feedback signal at their non-inverting emitter terminal.

[@saiebalrawi7890]

Hello, and thank you very much for your effort in simplifying the theory behind electronic circuits with all fine details, great job!
I've been working on a circuit that I inherited form an old design, it works but I am so puzzled trying to understand the theory behind it, can you help if I share it with you?
Thank you,

[@waynegram8907]

FESZ, make a video lesson about "leakage biasing" because this is what type of biasing was used in the 50s 60s because the transistors had leakage which you have to factor in the bias calculations

[@xDR1TeK]

Even real life doesn't work so well in real life 😂

[@michaelschwager786]

If I understand this correctly, do we assume that all components are the same temperature? So if the temperature rises on the main transistor, the other components follow?

[@FesZElectronics]

For temperature compensation, this behavior (having components at the same temperature) needs to somehow be ensured by design. For very low power (say a small signal amplifier), there should be no major temp difference - since there is no power dissipation; but for high power, it is common to put both the power element, as well as the compensation element in thermal contact - like have both tied to the same heatsink

[@CircuitShepherd]

👍😉

[@dankodnevic3222]

Also, you can put an cheap microcontroller to track emitter current (by ADC-ing voltage on resistor) and adjust bias on the base (gate), by DAC.

[@foobarables]

Any particular situation where this can be an advantage?

[@FesZElectronics]

I think it could be useful if the amplifier needs to have multilple operating modes - like low power (have bias current 1mA) high power (bias current 10mA); the uC could be used to switch between multiple references based on some other input

[@dankodnevic3222]

@@foobarables Many, apart from temperature stabilization, you could choose mode of operation for different input signal strength, power saving...

[@dankodnevic3222]

@@foobarables Also, compared with some techniques, reduction in number of components (if you already have CPU and some data bus).

[@foobarables]

@@dankodnevic3222 You will need something to measure temperature for which you need an ADC and some components, an ADC with interfacing components to measure the biasing state of the circuit in question and a DAC (or a simple PWM signal will do) with interfacing components and carefully crafted software to do the temperature compensation. But I like the idea of different operating modes as posted by Fesz. But also this can be implemented in other ways.

[@gamiwv]

Without a real circuit (at least on a breadboard) - -measured - all these are just for "chatting"