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8 votes
Accepted

Will this 3.3 V signal voltage be high enough to close Q3?

(Your current question title says 3.3 V while the text says 3 V, so I'll use the lower of the two.) Driving PWR_ENABLE with 3 V will be plenty to switch the whole ...
TonyM's user avatar
  • 23.5k
7 votes

Is my setup for a 5V motor project faulty?

You have the transistor "upside down." It should be like this: simulate this circuit – Schematic created using CircuitLab The arrow in the transistor symbol points towards ground. ...
JRE's user avatar
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3 votes
Accepted

Why does this transistor amplifier fail if Rc is greater than 50 ohms?

I wonder about accurate simulation of RF, using your current understanding of bipolar circuits. But I'll drop that and move on. A couple of bad things done in that ...
periblepsis's user avatar
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3 votes

Will this 3.3 V signal voltage be high enough to close Q3?

Q3 is a darlington pair, meaning that you require \$V_{BE}\approx 2\times0.7V = 1.4V\$ to switch it on. A potential of +3.3V at PWR_ENABLE will be adequate in this application, because collector ...
Simon Fitch's user avatar
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3 votes

Import transistor into LTSpice

Similar question has been answered here. You encountered an error because of a missing dot before the SUBCKT. I have corrected it in the script below. Save it in a ...
kaosad's user avatar
  • 1,198
2 votes

Finding relationship between saturation current and Vgs for MOSFET?

There's never a guarantee that a certain amount of current will flow, given some particular \$V_{GS}\$, because it varies so much even between devices from the same batch. Even if a datasheet does ...
Simon Fitch's user avatar
  • 38.8k
1 vote

Switching ON/OFF an ADC line

Well, there's a couple possibilities: Don't care. If the input currents are small enough, there's no wear on the ESD clamp diodes*, and VCC lifts imperceptibly against the normal loads on it (MCU ...
Tim Williams's user avatar
  • 39.6k
1 vote

4N25 Optocoupler design

You have a wee bit of an issue with a 100Ω load and this circuit. Generally you'd like the base current of the transistor Q2 to be 1/10 to 1/20 of the collector current, which argues for an R6 of ...
Spehro Pefhany's user avatar

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