How good is your scope? (problem with capturing offset signals)

Started by Klaus Kragelund in sci.electronics.design11 years ago 41 replies

Hi So I wanted to check the VCE of a transistor in a small converter running at 100kHz, expected to see about 100mV above ground as...

Hi So I wanted to check the VCE of a transistor in a small converter running at 100kHz, expected to see about 100mV above ground as the saturation voltage of the NPN, increasing linearely since magnetising current increasing. I saw nothing like that, debugging and found the scope (Tek DPO5000) somehow saturates with high voltage inputs. The signal is a square wave of 100kHz, 25V peak to...


Non Linear Resistor in LTspice

Started by Ricketty C in sci.electronics.design2 years ago 31 replies

I was looking at a simulation of a current regulator circuit to figure out why the voltage on a current sense resistor is not a nice sine wave-ish...

I was looking at a simulation of a current regulator circuit to figure out why the voltage on a current sense resistor is not a nice sine wave-ish like the applied voltage to the circuit. I expected a bit of distortion around the zero crossing points but otherwise a rectified sine wave. After mucking with the circuit thinking it had to do with transistor currents I realized the


Exceeding Vgs rating

Started by Pimpom in sci.electronics.design5 years ago 94 replies

I'm designing a small simple circuit in which a MOSFET drives a low-power load. The very low frequency gate drive may, on rare occasions,...

I'm designing a small simple circuit in which a MOSFET drives a low-power load. The very low frequency gate drive may, on rare occasions, exceed the max Vgs rating of 12V by about 1V, possibly 2V. There are a number of ways to limit the gate voltage but I want to avoid them and keep the circuit as simple as possible, and it won't cause a disaster if the transistor fails. What do you thi...


Low open loop gain from a mic preamp-why?

Started by amdx in sci.electronics.design11 months ago 36 replies

The only problem that I may have created is the transistor, I used BC547B with HFE of 200 to 450 vs BC549C with HFE of 420 to 800. All I had...

The only problem that I may have created is the transistor, I used BC547B with HFE of 200 to 450 vs BC549C with HFE of 420 to 800. All I had in my junk box. I built a low noise amplifier, original design was for a 30v supply, I chose to correct the values for a 15V supply. Designer does have a 12v version, my values are close.  I did set an emitter resistor to have equal clipping....


TO-92 vs sot-23 transistors for power

Started by Winfield Hill in sci.electronics.design7 years ago 67 replies

Q. Relative power dissipation capability of TO-92 transistor packages (viz, Zetex E-line parts) vs. sot-23 packages. More on this in my...

Q. Relative power dissipation capability of TO-92 transistor packages (viz, Zetex E-line parts) vs. sot-23 packages. More on this in my next post, first some background. One of my design interests is high-frequency, high-voltage power amplifiers. For example, I'm doing a 45V, 5A peak, DC-10MHz amplifier. My design uses 20 TO-220F power transistors, mounted on a 200W fan-cool...


Sloppy sine wave

Started by bitrex in sci.electronics.design7 years ago 5 replies

This is an about -30 dBu sine wave being amplified to about 0dBu by the triode section of a Sylvania 12EC8 triode/pentode "space charge" tube....

This is an about -30 dBu sine wave being amplified to about 0dBu by the triode section of a Sylvania 12EC8 triode/pentode "space charge" tube. The plate load is a single transistor gyrator/constant current source. Plate and heater currents are being supplied by a "China Special" boost converter module that's stepping up a 4 "C" cell battery pack. http://tinyurl.com/zeegduc Yick. Lots...


regulator thingie

Started by John Larkin in sci.electronics.design11 years ago 20 replies

I'm making some replacement boards for a system I designed a while ago. 1980, actually. The power regulator board used a couple of LM376's,...

I'm making some replacement boards for a system I designed a while ago. 1980, actually. The power regulator board used a couple of LM376's, a nice little DIP8 voltage regulator that drives an off-board heatsunk PNP pass transistor. LM376 seems to be unavailable. But I can't find a substitute, namely a linear voltage regulator controller with foldback capability and external PNP pass tr...


Emulating Open-Collector operation with TTL 74LS138...

Started by John Robertson in sci.electronics.design2 months ago 77 replies

Have a circuit that needs repair. Uses a TIP125 (NPN, Darlington) emitter tied to Vbb (~20VDC). Collector to load, then to ground. 1K resistor...

Have a circuit that needs repair. Uses a TIP125 (NPN, Darlington) emitter tied to Vbb (~20VDC). Collector to load, then to ground. 1K resistor (R1) pullup on Base to Vbb, and a second 1KR (R2) to the TTL controller. Problem is of course, that R2 puts the ~20VDC to the TTL output gate on a 74LS138. Trying to solve this without a driver transistor. The circuit is for a 1ms ~20V strob...


Any good books on heterogeneous junction transistors(HBT, HEMT etc.,(

Started by amal banerjee in sci.electronics.design7 months ago 1 reply

Could some transistor guru here plwase provide some pointers on this ? I am looking for some good books on heterogeneous junction transitors. It...

Could some transistor guru here plwase provide some pointers on this ? I am looking for some good books on heterogeneous junction transitors. It is odd that while heterogeneous transistors are replacing traditional homogeneous junction transistors in RF|microwave and high power switching applications, there is no good reference book on thse devices. All hints|suggestions will be greatly ap...


High voltage pnp's (250 volts)

Started by Hul Tytus in sci.electronics.design3 years ago 50 replies

sci.electronics.design, comp.arch.embedded high voltage pnp's (250v) Anyone know of a good pnp transistor spec'd up to 250 volts, a...

sci.electronics.design, comp.arch.embedded high voltage pnp's (250v) Anyone know of a good pnp transistor spec'd up to 250 volts, a probable current limit of 1 amp and designed as a switching device. It's to serve as the switcher in a variable frequency (pulse width held constant) power supply. So far a 2n2907 has been tried, with a 100ma 50 volt limit, with impressive results. Zete...


Question regarding class F amplifier efficiency

Started by amal banerjee in sci.electronics.design3 years ago

Could some electronics guru here please provide some hints. I am SPICE simulating a class F amplifier with 3, 5 and 7 harmonic tuning and an...

Could some electronics guru here please provide some hints. I am SPICE simulating a class F amplifier with 3, 5 and 7 harmonic tuning and an operating frequency of 500 MHz. I am using VFR92A as the transistor and measuring efficiency. The RMS output power is computed as : RMS output voltage x RMS output current across a resistor. The input DC power is measured as: RMS input DC current x...


LED driver

Started by Anonymous in sci.electronics.design3 years ago 28 replies

This is a single-cell, single inductor, single transistor LED driver. The values are all my first wild guesses, none tuned or tweaked, so...

This is a single-cell, single inductor, single transistor LED driver. The values are all my first wild guesses, none tuned or tweaked, so it could be improved. Efficiency is 70% with 1.6 mW into the LED. Version 4 SHEET 1 880 680 WIRE -144 64 -208 64 WIRE -16 64 -64 64 WIRE 80 64 -16 64 WIRE 240 64 160 64 WIRE 336 64 240 64 WIRE 400 64 336 64 WIRE 480 64 400 64 WIRE 336 112 336 ...