ECE3400 Lecture 29: Two-BJT Current Sources (Analog Electronics, Georgia Tech course)
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- Опубліковано 22 лип 2024
- Reference: leachlegacy.ece.gatech.edu/ec...
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0:00 -- Introduction
0:58 -- Two-BJT current source
4:36 -- Boring algebra
8:57 -- Output current
9:17 -- Special case
11:24 -- Output impedance
13:49 -- PNP version
14:13 -- Design procedure
14:56 -- Cascode current source
15:56 -- Opamp+BJT current source
re: Art of Electronics - I've got 2nd and 3rd editions, and it looks like the section on improving current sources has been moved to the "X-Chapters" accompanying volume, rather than kept with the main text.
Hi Eric. I can see I influenced your videos. Thank you for the admiration and respect you have for my channel. I appreciate you being my fan.
I’m a few videos into your lessons and I find them very interesting. I know that audio equipment doesn’t experience the very cold temperatures of industrial designs (-40C) but they do get hot. The Vbe multiplier will compensate for Vbe change over temperature (2 junctions) but no mention is made of this. The current sources are ok for small (ac) signals because their impedance would not change much but the currents sources are of little use if you need them to be constant over temperature. This is important for low power devices and for devices that have to start up reliably at both low and high temperatures. Resistors can be used to mitigate the effect to some extent but at the expense of higher voltages. Again, portable or low power devices may have only 3.3V or even less to work with and current sources/sinks have to be self compensating for the full operating temperature range (-40C to +85C).
The two-transistor source is not in TAoE3, but it's covered briefly in the 'X-Chapters' book, section 2x.2.1
Btw., yes, TAoE is a great book, it suffers from lacking Lantermans log through boring algebra a lot, though.
That was great
this is fly.
Thanks!
I just got a rash. I think its the algebra causing it. Well explained though!
9:58 a = 1, not 0
11:14 if you remove Re1 you got a whole lot of problems and you need to put resistor on the base of Q1 unless R1 (and Re2) is big enough. correct me if i'm wrong, but if the HFE is a model transistor is 100 you literally needs mA on the base of transistors dealing with voltages of 5, 12, 15 or similar voltages.
good thing multi meters exist.
You say "pretend {alpha} is 1", but then at 10:00, the slide 'Special Case' says"Let {alpha} = 0"
Your algebra isn't boring, you're just going too fast.
I can't read and follow it all while listening and then this cutscene of this bloke comes in distracting me from the whole thing.
I'm a schematic reading computer by now and know a lot of building blocks but by the time I'm figuring out what parts the terms in the formula relate to and how they're being manipulated they're already of the screen.
It's a very tricky balance in terms of how to present things on the video. I expect people to stop and start the video at the places they would like to spend more time. I've experimented with various approaches; if you look at my ECE3084 where I handwrite Khan academy style I go through things like algebra a lot more slowly.
I have a ton of data from UA-cam analytics, and generally found that if I go through algebraic things in a lot of detail, watch times totally drop off a cliff. The little clips may not be liked by everyone, but again, looking at the analytics, on average I've found that they seem to wake people up and keep people's attention.
I can very well imagine that
Maybe it's also just my overly interested ADD ass that can't focus on anything in the first place. Well except for designing and building things that is. I do love all your videos but it may be just me, liked the in depth in the Khan style but couldn't focus with the colours and writing and these I can very well follow the visible information but now I can't keep up. Guess it's just my all over the place brain. Used to have the same in class with everything but physics and chemistry where I couldn't focus because I kept designing devices in my head.
And I had a hard time with algebra due to concentration problems in class as well in a similar way as during these videos so it might be just me, the interruptions are very distracting and throw me way off but the videos are very good and clear apart from that.
And now I'm back to read the second half because it somehow popped out of my screen. Oh and I have before I think but I do want to thank you very much for these videos.
Especially the fuzz one with the original fz1 was very well timed as I had just decided to build one the day before instead of the regular synthesizer designing.
And that's crazy, how can you not be interested in algebra, or mathematics for that matter.
How else can one expect to be able to do something😮
It may not be the most fun thing, unless you solve a particularly shitty equation, but it's what makes the world go round.
Would be awesome though to have a course like this in my country so I wouldn't have to emigrate. Haven't missed a thing so far