Mixed Power Voltages in unipolar linear transistor amp?

Thread Starter

johnyradio

Joined Oct 26, 2012
208
Is it normal and for different components in the same circuit to have different voltages at the collectors?
  • For example, say i have a CMOS chip powered by +5V.
  • It outputs a 0V to 5V square wave.
  • Now i want to amplify that wave to 0V to 10V with a BJT.
  • Therefor i'll need to put 10V at the BJT power pin ("power pin" depends.on BJT config)
Correct?
 
Last edited:

cmartinez

Joined Jan 17, 2007
6,593
Is it normal and for different components in the same circuit to have different voltages at the collectors?
  • For example, say i have a CMOS chip powered by +5V.
  • It outputs a 0V to 5V square wave.
  • Now i want to amplify that wave to 0V to 10V with a BJT.
  • Therefor i'll need to put 10V at the BJT collector.
Correct?
Correct. But if you want an output of exactly 10V you may need to use a slightly higher voltage due to losses, depending on how you design your circuit. Also, you may need to use a level shifting arrangement to drive the BJT using the CMOS' output. Why don't you post a diagram of what you have in mind, so as to have a clearer picture?
 

Thread Starter

johnyradio

Joined Oct 26, 2012
208
thx for replies.
  • Input: 20-80 kHz staircase (i mispoke, it's not a simple square), positive-only, 0v to 5v
  • output: 0v to 10v, 10 uA
  • Hoping for low-parts count.
not sure which config is best.
  • Common Collector: voltage gain is about 1, right? i want gain of 2, so no good.
  • Common Base: very large voltage gain, but little current-drive, right?
  • Common Emitter: best of both worlds, but more parts?
This gives me output, but seems to go from 5V to 10V, instead of 0V to 10V

 
Last edited:

cmartinez

Joined Jan 17, 2007
6,593
thx for replies.
  • Input: 20-80 kHz staircase (i mispoke, it's not a simple square), positive-only, 0v to 5v
  • output: 0v to 10v, 10 uA
  • Hoping for low-parts count.
not sure which config is best.
  • Common Collector: voltage gain is about 1, right? i want gain of 2, so no good.
  • Common Base: very large voltage gain, but little current-drive, right?
  • Common Emitter: best of both worlds, but more parts?
This common-emitter gives me Max Current Exceeded, so i'm doing something wrong. Maybe cuz trying to drive with V instead of I?


http://tinyurl.com/y9w2ugmc
Add a 10k resistor between the frequency source and the transistor's base, so as to limit the current.
 

Thread Starter

johnyradio

Joined Oct 26, 2012
208
Last edited:

Thread Starter

johnyradio

Joined Oct 26, 2012
208
Does it have to be transistors? 1 opamp and two resistors will do the same job.
2:16 "You may say, 'i can just use an op am, put in feedback to set the gain and i'll be done.' You could, but an op amp, unless you buy a very good one, an expensive one, is going to have a lot of noise. A very low-noise op amp can be quite expensive. But if i were to use a single stage bipolar amplifier, it's going to have very little noise, it's going to be significantly cheaper, and plus we get to design it."

Now if i can only figure it out :D

 

Bordodynov

Joined May 20, 2015
2,418
I wish you success, but I doubt your success, unless of course you greatly change the requirements for the scheme.I'm pretty clever circuitry, but you did not like my solution on transistors.In addition, not the fact that the transistor circuit will be less noise.When you invent the scheme, I can (if you wish) calculate the noise.
 

Thread Starter

johnyradio

Joined Oct 26, 2012
208
I doubt your success, unless of course you greatly change the requirements
Which requirements?

I'm pretty clever circuitry, but you did not like my solution on transistors.
I can see you are very clever with circuits! I like your solution. Maybe I want the impossible :)

, not the fact that the transistor circuit will be less noise.
Unclear. Do you agree a transistor circuit will have less noise than op amp?

When you invent the scheme, I can (if you wish) calculate the noise.
Wow, many thanks, @Bordodynov!
 
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