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1 vote

Switching 600 V, 5 A with >100 megohm isolation

A relay is best: not only is the on/off ratio much higher*, it counts as physical separation between conductors. Only a sufficiently high voltage surge can jump the gap; the standoff rating is ...
Tim Williams's user avatar
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1 vote

BJT not switching properly

If D13 zener voltage is less than VDD_IN, then R8 will turn on Q10 and a very large current will from from VDD_IN through D13 and Q10. This will cause heating in D13 an Q10, which may damage one or ...
Fabio Barone's user avatar
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2 votes

Calculation of transistor values using hFE

Since I am using an LTspice simulation, I don't need to worry about burning the transistor out, nor about self-heating affecting the results- the junction will sit magically at 27°C even though it is ...
Spehro Pefhany's user avatar
2 votes

Calculation of transistor values using hFE

Perhaps you are overestimating \$V_{BE}\$. If, as you say \$I_C\approx I_E = 4.2mA\$, then for a 2N2222 with \$\beta\approx100\$, you would expect base current of: $$ I_B = \frac{I_C}{\beta}=\frac{4....
Simon Fitch's user avatar
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2 votes

Calculation of transistor values using hFE

Beta (or hFE) is a very loosely controlled parameter and can can vary by 10:1 over device to device, operation condition and temperature. In general a good design is done such that the circuit will ...
Kevin White's user avatar
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1 vote
Accepted

Do all SMPS ICs have an internal dead-time for the MOSFETs, specifically the LTC7878?

Those currents come from the reverse recovery of the body diode of the low-side MOSFET, which is the one driven by BG1 (if the config wasn't a sync buck then the ...
Rohat Kılıç's user avatar
0 votes

Unexpected output distortion when driving MOSFETs with SPWM in LTspice

Others have addressed the minutiae, I'll try and tackle the elephant in the room :) Why does the signal get distorted like this when I increase the frequency? What could be the reason for this? You'...
Kuba hasn't forgotten Monica's user avatar
0 votes

Driving Mosfets using NPN - PNP transistors in Ltspice

The whole exercise may be interesting but ultimately pointless. All you need is a single comparator with push-pull output. One chip. There's plenty of them to choose from. You absolutely must tell us ...
Kuba hasn't forgotten Monica's user avatar
3 votes
Accepted

Unexpected output distortion when driving MOSFETs with SPWM in LTspice

We want to reduce the gate voltage of the high side FETs to the source voltage, not necessarily ground. If I had to take a guess at the immediate issue, it may be that. I have a problem with a few ...
theph's user avatar
  • 156
1 vote

Unexpected output distortion when driving MOSFETs with SPWM in LTspice

Usually its the parasitics in the FET models. You can replace your FET model with ideal voltage controlled switches to double check. You can try putting a gate-source resistor on the high side FETs to ...
Gswffye's user avatar
  • 156
0 votes

4 wires from from power brick to 2 wire fixture

I had a different situation I have a 8kw Vevor Diesel Heater and I wanted to wire that to house mains to heat the house. I would recommend buying a power supply as per this video easier to see what is ...
Jason Robertson's user avatar
0 votes
Accepted

Controlling On/off of WL-134 Module with ESP32

If the RFID module requires 9V, but your control signal is 3.3V only, a simple BJT like S5080 won't do the job. One correct way is to use so-called HIGH-SIDE switch with Enable function, check Digi-...
Ale..chenski's user avatar
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0 votes

Power supply auto cut-off required when there is no audio signal

How to trigger the PAM8403 audio amplifier module when the clock chimes There are many details still unknown at this stage, but here are a few suggestions to help you - depending on exactly which ...
SamGibson's user avatar
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1 vote

Can a MOSFET be used for dimming instead of switching a LED?

I use this circuit in all of my LED lights. It has reverse voltage protection with some capacitor filtering on the power supply input. The potentiometer is used to alter the flow of current through ...
NuttyMonk's user avatar

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