Phil H MMIC as TIA

Started by Anonymous in sci.electronics.design2 years ago 1 reply

Phil, Have you ever considered using a darlington-type MMIC, like a Mini-Circuits part, as a fast photodiode TIA? Apart from scant specs, and...

Phil, Have you ever considered using a darlington-type MMIC, like a Mini-Circuits part, as a fast photodiode TIA? Apart from scant specs, and no Spice model, and ghastly DC behavior, it ought to work. They are cheap, stable, and super fast. Conventional opamp-type TIAs run out of speed low, and commercial ROSA-type things are mostly useless for DC-coupled applications. As you note in yo...


Bibtrex Howland

Started by Habib Bouaziz-Viallet in sci.electronics.design7 years ago 2 replies

Hello Bib, I drew my "bafouille" on this saturday morning .... no math, no excessive sims just fixed the fact that in your previous...

Hello Bib, I drew my "bafouille" on this saturday morning .... no math, no excessive sims just fixed the fact that in your previous schematics you miised that the opamp goes directly to vcc. try go further with e.g 1000Hz sine .... Good luck. Habib. PS : Version 4 SHEET 1 1052 804 WIRE 576 -144 416 -144 WIRE 976 -144 656 -144 WIRE -128 -16 -128 -48 WIRE 0 -16 0 -48 WIRE 624...


mux-friendly opamp

Started by John Larkin in sci.electronics.design3 years ago 37 replies

This amp http://www.ti.com/product/OPA2189 is mux-friendly and EMI hardened on its input. I wonder how mux friendly it is on its...

This amp http://www.ti.com/product/OPA2189 is mux-friendly and EMI hardened on its input. I wonder how mux friendly it is on its output. The compensation scheme (fig on page 18 of the data sheet) has Ccomp hanging on the output pin, like LM8261 which is c-load stable and pretty good driving multiplexers. Many opamps freak out driving multiplexers. That can cause weird errors and c...


LED output vs bias current

Started by George Herold in sci.electronics.design8 years ago 20 replies

So I was shinning some Cree leds onto a photodiode and measuring the photoc= urrent. Here=92s a plot (opamp bias current ~20pA subtracted from...

So I was shinning some Cree leds onto a photodiode and measuring the photoc= urrent. Here=92s a plot (opamp bias current ~20pA subtracted from data.) https://www.dropbox.com/s/atyo4uvsb09fgd7/LED-PD.BMP Below about 1mA of LED bias current the photo current increases as the 3/2 = power of the led current. Which was totally unexpected! (I expected linea= r.) I=92m making up a hand-waving ...


input/output crosstalk/noise in AC inverting amp

Started by Anonymous in sci.electronics.design3 years ago 5 replies

we have an inverting opamp as AC amplifier with gain 100 or 1000 in a shielded aluminum box. BNC as input and output. Using chopped light and...

we have an inverting opamp as AC amplifier with gain 100 or 1000 in a shielded aluminum box. BNC as input and output. Using chopped light and measuring noise on top of a signal with a lockin amplifier. I am wondering why different ops behave differently. We had it on the table so that input and output BNC crossed each other at ca. 90°. Not optimal, I know, so we rotated the al


+1/-1 gain stage

Started by George Herold in sci.electronics.design8 years ago 41 replies

Hi all, Just playing with ideas for a +1/ -1 switched gain stage for an opamp. https://www.dropbox.com/s/yzyc78zk5xqwa98/DSCF0017.JPG So the...

Hi all, Just playing with ideas for a +1/ -1 switched gain stage for an opamp. https://www.dropbox.com/s/yzyc78zk5xqwa98/DSCF0017.JPG So the first one just uses a double throw switch to switch the output. And then 2.) is the "classic" switched input. And then more games, https://www.dropbox.com/s/4ocqil9k0yo9ffm/DSCF0018.JPG And some more. (I could go on... :^) Any thoughts on t...


MDAC output amp

Started by John Larkin in sci.electronics.design4 years ago 2 replies

I'm going to use a DAC8812 MDAC to scale a sine wave amplitude. I need a lot of swing and need to drive a big capacitive load, and the...

I'm going to use a DAC8812 MDAC to scale a sine wave amplitude. I need a lot of swing and need to drive a big capacitive load, and the only opamp that I have that might work is THS6022. That's a 250 mA, 3 watt, 300 MHz current-mode amp. I didn't expect that to work, but it does: https://www.dropbox.com/s/fhyy19cf4b61fxa/THS3.asc?dl=0 https://www.dropbox.com/s/zebkvslk93vytwd/THS6022.L...


current-mode opamp noise

Started by John Larkin in sci.electronics.design5 years ago 8 replies

I need a fast, high slew, low noise amplifier with a precise gain of +3. The fastest opamps around are current-mode parts. They tend to have...

I need a fast, high slew, low noise amplifier with a precise gain of +3. The fastest opamps around are current-mode parts. They tend to have impressive voltage noise specs, but they have terrible DC specs and tons of current noise. Low open-loop gains, too. They usually have a required/optimum value of feedback resistor, so the inverting input current noise dumps into Rf and makes output ...


Opamp long term offset voltage drift

Started by Klaus Kragelund in sci.electronics.design8 years ago 21 replies

Hi I am involved in a design where we need long term stability. That means we need low long term offset drifts (we do production...

Hi I am involved in a design where we need long term stability. That means we need low long term offset drifts (we do production calibration) So, the OPA277 for example has 0.2uV/month (30uV initial offset) Checking out the datasheet for the MCP6286 shows initial offset of 1.5mV. What would be the best guess for long term drift of the offset? Or do we need to ask the manufactor? Che...


Amplifier with very low input- design search

Started by captoro in sci.electronics.design7 years ago 18 replies

Hello guys, I am building an extremely low input (voltage) amplifier, with about .2 volt spikes and also -0.2 volt spikes. I just need to...

Hello guys, I am building an extremely low input (voltage) amplifier, with about .2 volt spikes and also -0.2 volt spikes. I just need to detect if there is a voltage, either positive or negative then turn on a led when it is detected. My questions are as followes, - do I need negative supply ( in the case i use an opamp, i guess I will need +/- supply) - Why can I use at the input to inver...


Another opamp question

Started by Peabody in sci.electronics.design4 years ago 37 replies

Let's say I have an inverting amp with the + input at ground. The feedback resistor Rf is 100K, and the input resistor R1 to the inverting...

Let's say I have an inverting amp with the + input at ground. The feedback resistor Rf is 100K, and the input resistor R1 to the inverting input is 10K. That's a gain of -10. Now suppose I add R2, a 10K resistor from the inverting input to ground. It seems this would cut the input signal in half, and lower the input impedance, but doesn't change the gain. I say that because at virtua...


Unequivalent Input Impedance in Differential OpAmp Circuit

Started by Rick C in sci.electronics.design2 years ago 21 replies

I have an existing design that uses a single op amp stage with differential inputs and AC coupling caps on the inputs. The circuit acts as a 5:1...

I have an existing design that uses a single op amp stage with differential inputs and AC coupling caps on the inputs. The circuit acts as a 5:1 divider so the two input resistors are 51 kohms and the feedback resistor as well as the ground resistor in the non-inverting input leg are 10 kohms. The input caps are sized to maintain a good low frequency response. Many years ago I


Input-referred Resistor Noise Question

Started by Jim Thompson in sci.electronics.design6 years ago 3 replies

Suppose I have an OpAmp (a behavioral model ;-) that has a gm=1 driving a load resistor R, thus the voltage gain=R Thus am I correct in...

Suppose I have an OpAmp (a behavioral model ;-) that has a gm=1 driving a load resistor R, thus the voltage gain=R Thus am I correct in assuming that the input-referred noise from the load resistor, R, is so low as to be ignorable, thus I can avoid having to use a noiseless resistor model as the load? Am I correct that, in this case... VN_input-referred = 0.13/sqrt(R) nV/rt-Hz ? For...


current mirror

Started by John Larkin in sci.electronics.design6 years ago 15 replies

This seems pretty obvious, but I can't recall seeing it anywhere before. One opamp and two resistors! Version 4 SHEET 1 880 680 WIRE...

This seems pretty obvious, but I can't recall seeing it anywhere before. One opamp and two resistors! Version 4 SHEET 1 880 680 WIRE 80 -48 -128 -48 WIRE -128 16 -128 -48 WIRE 80 16 80 -48 WIRE 48 32 -32 32 WIRE 192 48 112 48 WIRE 336 48 192 48 WIRE 48 64 16 64 WIRE 80 112 80 80 WIRE -128 144 -128 96 WIRE 192 144 192 48 WIRE 336 144 336 48 WIRE -32 256 -32 32 WIRE 192 256 ...


strange second-order active lowpass filter

Started by Anonymous in sci.electronics.design7 months ago 8 replies

This is a new-to-me lowpass topology, roughly 2nd order Bessel. The final RC stomps opamp high-frequency noise. Version 4 SHEET 1 880...

This is a new-to-me lowpass topology, roughly 2nd order Bessel. The final RC stomps opamp high-frequency noise. Version 4 SHEET 1 880 680 WIRE 96 32 48 32 WIRE 656 32 160 32 WIRE 368 112 336 112 WIRE 336 144 336 112 WIRE -160 160 -224 160 WIRE -96 160 -160 160 WIRE 48 160 48 32 WIRE 48 160 -16 160 WIRE 304 160 48 160 WIRE 448 176 368 176 WIRE 480 176 448 176 WIRE 512 176 480 176...


boosted opamp

Started by Anonymous in sci.electronics.design2 years ago 8 replies

This might work: Version 4 SHEET 1 1080 680 WIRE 64 -48 -144 -48 WIRE 400 -48 64 -48 WIRE -144 -16 -144 -48 WIRE -416 0 -512 0 WIRE...

This might work: Version 4 SHEET 1 1080 680 WIRE 64 -48 -144 -48 WIRE 400 -48 64 -48 WIRE -144 -16 -144 -48 WIRE -416 0 -512 0 WIRE -288 0 -336 0 WIRE 400 0 400 -48 WIRE -512 48 -512 0 WIRE 336 48 304 48 WIRE -144 96 -144 64 WIRE 64 96 64 -48 WIRE 32 112 -32 112 WIRE 144 128 96 128 WIRE 176 128 144 128 WIRE 256 128 240 128 WIRE 304 128 304 48 WIRE 304 128 256 128 WIRE 400 12...