8
votes
Base and emitter pins of BJT swapped
If I understood your problem properly, you have in your PCB pins 2 and 1 swapped, like this, but the BJT is as the diagram in your question shows:
In that case, I would try to un-solder the BJT and ...
- 127
6
votes
Solenoid driver circuit with peak hold
advantage of the BJT could be to choose a base current so the BJT also could be used as a current limiter
It doesn't matter much if it would be a BJT or a MOSFET, since the control of the current has ...
6
votes
Solenoid driver circuit with peak hold
Below is the LTspice sim of a PWM Hit & Hold circuit for the solenoid:
It uses a CD4093 quad Schmitt-trigger NAND gate to generate a 10kHz PWM signal, which holds the solenoid at 10mA after the ...
- 429
5
votes
Accepted
Power latching circuit MOSFET is stuck ON
Power latching circuit MOSFET is stuck ON
It's not stuck on. You've wired the P channel MOSFET incorrectly.
The body diode will always conduct giving you the impression that it is "stuck on&...
- 467k
4
votes
Base-emitter reverse breakdown and current
So my question is: considering that I'm breaking the absolute maximums here, what is the danger of the transistor actually breaking/degrading significantly?
I just ran some tests with 2N3904 ...
- 26.1k
4
votes
Why use diode connected BJT (and not just connect two BJT back-to-back) for current mirror circuit?
The whole point of using another BJT with identical characteristics, is that they both agree on what \$V_{BE}\$ needs to be present in order to pass exactly 1mA, or any current.
Your assumption that ...
- 42.2k
2
votes
RC Phase Oscillator Resistor placement
The second circuit doesn’t oscillate because there’s no feedback, you’ve connected C1 directly to your supply voltage.
- 26k
2
votes
Current measurement with c BJT current mirror
Just change some resistor's values ...
Note that the change of resistor of 50 Ohm is very "critical".
Simulated at two temperatures with microcap v12.
Gain is calculated with (my) R2/R1 (To ...
- 15k
2
votes
Accepted
Current measurement with c BJT current mirror
By using 0.1 ohm shunt at 2A the drop across shunt is 0.2V.
Setting gain of T1 with Rc/Re ratio to 21 you are getting 4.2V Vcurr (at 2A).
You cannot set the circuit to output full 5V Vcurr since there ...
- 2,300
1
vote
Positive and Negative Voltage Buffers with Current Buffers
It's not generally bad to reverse bias the base-emitter junction, and doing so doesn't automatically damage the transistor, unless that causes excessive power dissipation. There is apparently some \$\...
- 42.2k
1
vote
Accepted
Why can you multiply gains from different points to get a final gain?
We can treat it as a black box.
simulate this circuit – Schematic created using CircuitLab
We can treated as a black box. We know that the Rin of this box is Rc + re2. Thus, the Q1 collector ...
- 15.4k
1
vote
Why does current mirror need a diode connected configuration?
Short answer
Connecting a transistor's gate to its drain introduces negative feedback, reversing its operation. Instead of converting voltage to current, it now converts current to voltage. By ...
- 18.2k
1
vote
Why use diode connected BJT (and not just connect two BJT back-to-back) for current mirror circuit?
Short answer
Connecting a transistor's base to its collector introduces negative feedback, reversing its operation. Instead of converting voltage to current, it now converts current to voltage. By ...
- 18.2k
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