MC6566 Equivalent WITHOUT Hysteresis

Started by Jim Thompson in sci.electronics.design4 years ago 21 replies

I have a situation, somewhat like Klaus', where I need to (purposefully) use a comparator as a quasi-OpAmp. An MCP6566 fits the bill as to...

I have a situation, somewhat like Klaus', where I need to (purposefully) use a comparator as a quasi-OpAmp. An MCP6566 fits the bill as to speed, open-drain output, and low supply requirements. What I need is an MCP6566 look-alike EXCEPT no hysteresis. Suggestions? ...Jim Thompson -- | James E.Thompson | ...


How about it? Experiments of the third kind , take 999999.

Started by Jan Panteltje in sci.electronics.design10 years ago 2 replies

How about it? Experiments of the third kind , take 999999. Update opamp and PIC power supply design: part 1 ...

How about it? Experiments of the third kind , take 999999. Update opamp and PIC power supply design: part 1 PNP --------------------------- e c--------------------------------------------------------------- + 3.5V +/- 1mV @ 20mA noise free to PIC and EEPROMS. | | b Q1 | | | ...


lm358-like opamps

Started by Bill Martin in sci.electronics.design10 years ago 12 replies

Hi, anyone have a favorite brand/flavor of lm358 or equivalent opamp to recommend for a simple, low performance integrator to generate a...

Hi, anyone have a favorite brand/flavor of lm358 or equivalent opamp to recommend for a simple, low performance integrator to generate a voltage ramp? 0.5 to 2.5 volts, supply voltage available up to 18V. About one to two seconds duration, no repeating..one shot style. Looking at just Mouser, there seem to be 23 parts in soic-8 to choose from... Thanks, Bill Martin


LTSpice: Slow on noise sims with foreign opamps

Started by Joerg in sci.electronics.design9 years ago 79 replies

Folks, Yahoo has made the sign-in procedure so onerous (can't get in anymore) that I'll ask here instead of the LTSpice group: I want to do...

Folks, Yahoo has made the sign-in procedure so onerous (can't get in anymore) that I'll ask here instead of the LTSpice group: I want to do some noise simulations, for example with a TI opamp in there. Loading the complete model it spends forever in the stepping phase, then pseudo-damped analysis and whatnot. Is there any way this can be sped up? All I need to see is ballpark where th...


OpAmp Feedback Resistance vs. Stability

Started by Tim Wescott in sci.electronics.design5 years ago 15 replies

So, about a decade and a half ago, I worked with some very ill-tempered rail-rail opamps. They were among the first-generation rail-rail amps,...

So, about a decade and a half ago, I worked with some very ill-tempered rail-rail opamps. They were among the first-generation rail-rail amps, and they had the "nice" feature that in spite of their specified behavior, they'd go unstable as a voltage follower if you just connected the output to the negative input -- but they'd work fine if you did so through a 1k-ohm resistor. I got i...


Never Buy Maxim (again)

Started by John Larkin in sci.electronics.design8 years ago 130 replies

Maxim makes an opamp, MAX44280, that has a specified input capacitance of 0.4 pF. That would be great in some apps where Cin causes...

Maxim makes an opamp, MAX44280, that has a specified input capacitance of 0.4 pF. That would be great in some apps where Cin causes noise-gain peaking. I figured I'd give Maxim another chance, after being s*****d by them in the past. So I went online and filled out their sample request. The process makes no sense, website runaround, but eventually I got it done. Two days later I go...


opamp input capacitance

Started by John Larkin in sci.electronics.design8 years ago 33 replies

I see opamps that specify "differential" and "common-mode" input capacitance, but don't say what that really means. An extreme case is...

I see opamps that specify "differential" and "common-mode" input capacitance, but don't say what that really means. An extreme case is ADA4817-1, where Ccm is 1.3 pF and Cdiff is 0.1! Any ideas? If I use this as a classic inverting amp, with the + input grounded, what would the capacitance look like at the - input? (I'm being pressured to get a proposal out, with specs and pricing, so...


Back emf when unplugging coil?

Started by George Herold in sci.electronics.design2 years ago 19 replies

Hi all, I've got a coil driver 3 amps max. coils are ~10 ohms and I'd have to look up the inductance... big open air coil. So a user had a...

Hi all, I've got a coil driver 3 amps max. coils are ~10 ohms and I'd have to look up the inductance... big open air coil. So a user had a problem and it looks like the pass transistor blew. (2N6059... I did this design ~15-20 years ago.) The circuit is a simple opamp voltage to current converter. And has never had problems before (that I know of.)* So the tech at the school who is r...


TCA0372 troubles

Started by George Herold in sci.electronics.design2 years ago 36 replies

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately I've blown it up three times... twice by accident and this morning on...

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately I've blown it up three times... twice by accident and this morning on purpose. Apparently the TCA can't have it's output shorted to ground. I_out max is 1.0 A (DC), https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF So I need either some output protection.. current limit. Or another opamp that does ~100 mA, or I'll...


Multiple regulated voltages

Started by Piotr Wyderski in sci.electronics.design2 years ago 35 replies

I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). I was shocked that it is virtually impossible to find a negative...

I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA). I was shocked that it is virtually impossible to find a negative voltage LDO capable of hundreds of milliamps and reasonably cheap. It seems that producing all these rails with a bunch of opamp-boosted emitter followers will be cheaper than a single adjustable negative LDO. I already have a decent 2.5V reference (LTC6655) i...


speaking of substrate diodes...

Started by Anonymous in sci.electronics.design1 month ago 2 replies

leads to this one... https://www.dropbox.com/s/cgaxalnn3hhf315/RRIO_Logamp.jpg?raw=1 where we use the substrate diode of a RRIO opamp as a...

leads to this one... https://www.dropbox.com/s/cgaxalnn3hhf315/RRIO_Logamp.jpg?raw=1 where we use the substrate diode of a RRIO opamp as a logarithmic current-to-voltage converter. There are better ways to do this, but maybe none so cute. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable whe...


C-multiplier again

Started by John Larkin in sci.electronics.design11 years ago 137 replies

I need a super-low noise power supply. I have a 15 volt switching wall-wart input and want as close to 15 volts, regulated, as I can get;...

I need a super-low noise power supply. I have a 15 volt switching wall-wart input and want as close to 15 volts, regulated, as I can get; 14 would be nice, 13.5 is OK. The LDOs that I can find are all pretty noisy and have mediocre PSRR. So I thought about using a Phil Hobbs-ian c-multiplier transistor, an R-C lowpass and an emitter follower, with a slow opamp loop wrapped around i...


why do they do this?

Started by John Larkin in sci.electronics.design2 years ago 132 replies

ST makes a nice little LDO, super-low dropout with an aux Vbias supply. Saves me from rolling my own with an opamp and a mosfet. It's an...

ST makes a nice little LDO, super-low dropout with an aux Vbias supply. Saves me from rolling my own with an opamp and a mosfet. It's an ST1L08. So why is the data sheet file en.DM00123507.pdf ? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com


SPICE deep yogurt..

Started by Robert Baer in sci.electronics.design7 years ago 37 replies

Well, according to the "help" document, there should be a "Draw" on the top selection bar; NOPE! So i have no idea as to draw a new part...

Well, according to the "help" document, there should be a "Draw" on the top selection bar; NOPE! So i have no idea as to draw a new part and label it. Therefore i hope i have an invisible LM185ADJ, and hoped it would work... I "broke out" the various subcircuits (transistor, opamp, and even the LM185ADJ) then drew a "test" circuit to probe. Very deep dodo...help? Version ...


opa145

Started by George Herold in sci.electronics.design2 years ago 19 replies

Hi all, Well the opa124 is EOL, suggested replacement is opa145. http://www.ti.com/lit/ds/symlink/opa145.pdf Looks nice. Very low 1/f noise...

Hi all, Well the opa124 is EOL, suggested replacement is opa145. http://www.ti.com/lit/ds/symlink/opa145.pdf Looks nice. Very low 1/f noise corner. And then I got a little worried looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then the graph ends at 100 kHz. Anyone looked at used this opamp? I'm going to order a few. Thx George H.


LTspice Tip

Started by Jim Thompson in sci.electronics.design6 years ago 10 replies

As I work my way to a Universal OpAmp Spice Model that you only have to feed the subcircuit 10-12 numbers from the datasheet, I observe that...

As I work my way to a Universal OpAmp Spice Model that you only have to feed the subcircuit 10-12 numbers from the datasheet, I observe that LTspice struggles with what I would consider ordinary hyperbolic functions (bounded, all derivatives exist, are finite, and continuous)... making a straight line out of a transfer curve with soft limiting on each end... and churning... churning... churni...


Level shifter /opamp voltage booster?

Started by George Herold in sci.electronics.design5 years ago 34 replies

Hi all, not really sure what to call this. (Or I'd search the web and find something.) I'm sending about 50 watts to a heater (~50V @1 amp.) ...

Hi all, not really sure what to call this. (Or I'd search the web and find something.) I'm sending about 50 watts to a heater (~50V @1 amp.) I was going to do a current control thing, (see top pic here.) https://www.dropbox.com/s/w7lizyl47rdkzp8/levleshift.JPG?dl=0 But that puts about 1W into the current sense resistor at max power. So I drew the bottom drawing, with a transistor to ...


semiconductor drift

Started by John Larkin in sci.electronics.design7 years ago 52 replies

We have two 8-channel waveform generators that were shipped 4 months ago, and came back because the customer ordered too many or something. We...

We have two 8-channel waveform generators that were shipped 4 months ago, and came back because the customer ordered too many or something. We routinely test anything that comes back, before returning them or returning to stock. What's interesting is that all 16 channels have a negative DC offset. Each channel is a diff-current-output cmos DAC, an opamp diffamp, a passive LC filter, and ...


simple opamp amplifier circuit

Started by panfilero in sci.electronics.design9 years ago 23 replies

I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offset, but if I don't include a capacitor on my input my output hits the...

I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offset, but if I don't include a capacitor on my input my output hits the rails... why is this? The link shows what I'm doing in LTSpice thanks http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg


signal pickoff

Started by John Larkin in sci.electronics.design6 years ago 65 replies

I'm designing a high-voltage pulser, 1200 volts or so, and I'd like to pick off a divided signal for the customer to...

I'm designing a high-voltage pulser, 1200 volts or so, and I'd like to pick off a divided signal for the customer to monitor. https://dl.dropboxusercontent.com/u/53724080/Circuits/Resistors/Pickoff.JPG Rise/fall times will be a few us maybe. I'd like to have the pulse response be pretty good, so the capacitances matter. The OPA171 opamp and R2 have capacitance, roughly 4 pF total, ...