Voltage dropper

Started by George Herold in sci.electronics.design4 years ago 19 replies

Hi all, so still futzing with my 'power' bipolar current source. here...

Hi all, so still futzing with my 'power' bipolar current source. here , https://groups.google.com/forum/?fromgroups=&hl=en#!topic/sci.electronics.design/XHnLmIX6dhY I made a voltage dropper with a string of 1n4002's (5) to reduce the negative rail on the INA134. This let me move the power opamp back inside both loops. (I think this is better 'cause it gets rid of any offsets caused by...


tacky signal detector

Started by John Larkin in sci.electronics.design3 years ago 2 replies

We'd like to light up an LED when the customer gives us an input, nominally 1 volt peak at 10 MHz, but could be less. This detector might...

We'd like to light up an LED when the customer gives us an input, nominally 1 volt peak at 10 MHz, but could be less. This detector might work. It depends on schottky diode leakage to discharge the cap. It will drive an opamp, or a comparator, with pA bias current. We'd threshold that at 20 mV or some such to turn on the LED. Version 4 SHEET 1 880 680 WIRE -304 96 -576 96 WIRE -96...


different opamp gains based on sign?

Started by DemonicTubes in sci.electronics.design5 years ago 4 replies

I've got a differential signal, however, the negatives are small and interesting while the positives are large and less interesting (but still...

I've got a differential signal, however, the negatives are small and interesting while the positives are large and less interesting (but still important). Is there an amplifier topology that allows me to set a larger gain for negative signals and small gains for positive signals? Need to be able to measure the 'positive' signals which can be as high as 80mV, but I am more interes


low current inverter

Started by George Herold in sci.electronics.design8 years ago 121 replies

low current +5V -> -5V (-3.5V?) inverter. I've got a few unused 74HC14's on a digital ciruit. (maybe I can turn these digital dogs to an...

low current +5V -> -5V (-3.5V?) inverter. I've got a few unused 74HC14's on a digital ciruit. (maybe I can turn these digital dogs to an analog purpose?) I just need a few mA's to pull an opamp rail below gnd. (OK a Cui dc-dc converter is on order from DK, for $4-5 it's hard to resist.) But how to make a +/- inverter from a few 14's? So I started with the classic inverter RC bang-ban


AM antenna

Started by George Herold in sci.electronics.design10 years ago 33 replies

AM antenna. (proving yet again that a little knowledge can be a dangerous thing.) I've been reading Terman's "Radio Engineer's Handbook" *...

AM antenna. (proving yet again that a little knowledge can be a dangerous thing.) I've been reading Terman's "Radio Engineer's Handbook" * on antenna's, and Charles Wenzel's web site, http://www.techlib.com/electronics/antennas.html (The only useful thing I could find on the web.) My previous AM antenna was a ~10 foot piece of stranded wire (0.05" diam.) stuck into an inverting opamp. ...


TSH93

Started by pw in sci.electronics.design8 years ago 3 replies

Hi, I'm trying to add to LTspice IV TSH93 opamp (in the schematic as opamp2), but without success, a message appears: Port(pin) count...

Hi, I'm trying to add to LTspice IV TSH93 opamp (in the schematic as opamp2), but without success, a message appears: Port(pin) count mismatch between the definition of subcircuit "tsh93" and instance: "xu4". The instance has fewer connection terminals than the definition. In the lib\sub added TSH93.sub file: ** Standard Linear Ics Macromodels, 1997. ** CONNECTIONS : * 1 INVERT...


Opamps as voltage sources (C-loading)

Started by George Herold in sci.electronics.design3 years ago 23 replies

So I've got this lmxxx (317, x05) voltage bias source.. (V bias = 5V, 5ma max. i'm loading it ) that I can put in some corner of this circuit...

So I've got this lmxxx (317, x05) voltage bias source.. (V bias = 5V, 5ma max. i'm loading it ) that I can put in some corner of this circuit board. Or there's this left over opamp, (I think it's like a 5mA max for the sensor, and I'm loading it much less than that... (maybe I should try more R?) Anyway, I was thinking about JL, and with more C-load it got 'better' again. And searchi...


Voltage limits

Started by George Herold in sci.electronics.design10 years ago 40 replies

I need to keep an opamp derived voltage limited to between 1 and 5 volts. The limits are a bit loose. So a swing to 0.85 volts or up to 6.0...

I need to keep an opamp derived voltage limited to between 1 and 5 volts. The limits are a bit loose. So a swing to 0.85 volts or up to 6.0 volts is fine. I drew this up with opamps driving diodes at the correct voltages. But the opamps seemed like over kill. So I=92m thinking of using a three terminal adjustable voltage regulator. I then had the brilliant (or stupid) idea of using the...


emi hardened opamps

Started by John Larkin in sci.electronics.design4 years ago 27 replies

We have an ADC board that uses LT1124 opamps in the front end. In fact, the circuit is in AoE3, page 361, somewhat modified by Win. One...

We have an ADC board that uses LT1124 opamps in the front end. In fact, the circuit is in AoE3, page 361, somewhat modified by Win. One customer likes the product but is seeing offsets, 10s of microvolts, from EMI, mostly digital spikes in the VME crate. I guess the opamp front ends are rectifying stuff, even though we have beads and caps to keep obvious-path RF out. So we'd like to ...


opamp switchable gain

Started by Clive Arthur in sci.electronics.design4 years ago 41 replies

I have a standard inverting op-amp with a 1k input resistor. The feedback comprises one fixed resistor with three more parallel resistors...

I have a standard inverting op-amp with a 1k input resistor. The feedback comprises one fixed resistor with three more parallel resistors which can be connected or disconnected by analog switches, giving 8 possible gain settings. I want a minimum gain of 1 and a maximum of 20. (ok, -1 and -20, it's inverting) Clearly, the fixed resistor should be 20k to give a gain of 20 with all ...


Smooth Clamp Question

Started by Jim Thompson in sci.electronics.design5 years ago 26 replies

Trying to smooth the abruptness of a classic OpAmp clamp circuit... Any ideas? Thanks! ...

Trying to smooth the abruptness of a classic OpAmp clamp circuit... Any ideas? Thanks! ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Disc


HV control

Started by George Herold in sci.electronics.design4 years ago 66 replies

Hi all, another circuit fumble on my part. I copied this circuit fragment from whit3rd... part of thread is pasted in below. Here's the...

Hi all, another circuit fumble on my part. I copied this circuit fragment from whit3rd... part of thread is pasted in below. Here's the circuit I built. https://www.dropbox.com/s/skaspzjafoqmcfl/HV-control.JPG?dl=0 I ground the base of Q2 and added R3 so that it would start out with the HV turned off. D1 was added because I was worried about the zenering Q2's base. (opamp has...


New Behavioral Spice Model Posted

Started by Jim Thompson in sci.electronics.design7 years ago 1 reply

A convenient element to approximate input-referred noise in an OpAmp Spice model. Just insert in series with one input, set en (noise floor) &...

A convenient element to approximate input-referred noise in an OpAmp Spice model. Just insert in series with one input, set en (noise floor) & Fn (1/F corner). See... InputReferredNoise.zip on the Device Models & Subcircuits Page of my website. ...Jim Thompson -- | James E.Thompson | mens | |...


Phototransistor fed to a transimpedance amplifier

Started by SilverLeo in sci.electronics.design6 years ago 45 replies

Hi all. I'm running through some test of a phototransistor signal conditioner, and I'm facing with wild noise issues. The conditioning is a...

Hi all. I'm running through some test of a phototransistor signal conditioner, and I'm facing with wild noise issues. The conditioning is a basic TIA stage: http://i.imgur.com/PcgglKZ.png Feedback resistor is 5K, feedback capacitor is 470pF, negative bias is -12V, and photocurrent is in the range 8uA-800uA. The bandwidth should be about 50kHz. Opamp is OPA2277UA. Problem is that phototrans...


CMOS opamp 18V+, RR in and DIP-14?

Started by Joerg in sci.electronics.design7 years ago 26 replies

Gentlemen, Got an EMI (susceptibility) situation, existing design from a vendor, no major changes possible at this point other than 1:1...

Gentlemen, Got an EMI (susceptibility) situation, existing design from a vendor, no major changes possible at this point other than 1:1 component swaps. It's a quad DIP-14 in standard pinout. Bipolar right now which is EMI-prone so it has to be CMOS. JFET amps are out because we need the input range down to the negative rail and they can't do that. CMOS for 18V and higher is slim pic...


OT: Integrator Windup and Spice Modeling

Started by Jim Thompson in sci.electronics.design6 years ago 5 replies

Musing over a generic full-featured OpAmp Spice model and how to quantify integrator/compensation windup... How would you quantify windup? ...

Musing over a generic full-featured OpAmp Spice model and how to quantify integrator/compensation windup... How would you quantify windup? Recovery _times_ from positive or negative headroom, or some other quantification? Thanks! ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations ...


Low voltage virtual ground

Started by garyr in sci.electronics.design9 years ago 4 replies

I need a half-rail virtual ground in a 3.3 volt circuit. I couldn't find anything like a TLE2426 that would work at that voltage so I thought I...

I need a half-rail virtual ground in a 3.3 volt circuit. I couldn't find anything like a TLE2426 that would work at that voltage so I thought I would use a low-voltage opamp configured as a follower with VCC/2 connected to the positive input. The TI LMV721 has a supply voltage range of 2.2 to 5.5 volts and a GBW of 10 MHz. That would be probably be acceptable but I would like to extend the ...


Filtering switcher noise

Started by bitrex in sci.electronics.design6 years ago 15 replies

I'm putting together a little 4-> 1 active audio mixer circuit for a friend of mine. The circuit is basically just RC RF filter on the...

I'm putting together a little 4-> 1 active audio mixer circuit for a friend of mine. The circuit is basically just RC RF filter on the input, dc blocking capacitor, potentiometer, then into an active summer and a "zero impedance" output stage for driving cable that has a capacitive feedback loop to keep the opamp stable and then a second feedback loop around the output resistor for st


Differential PWM filter

Started by bitrex in sci.electronics.design6 years ago 1 reply

Say I have 2 or 3 PWM channels coming out of a FPGA or microcontroller or something, and I want to filter and sum them into one analog...

Say I have 2 or 3 PWM channels coming out of a FPGA or microcontroller or something, and I want to filter and sum them into one analog output. Is there any advantage to using 4 or 6 output lines and using an opamp in a differential summer/two pole filter configuration, over using a single ended summer/filter?


Opamps with inversion problem.

Started by Anonymous in sci.electronics.design3 years ago 16 replies

I wonder if perhaps I could make good use of the inversion bug, using it to extinguish outputs without the usual extra circuitry required when...

I wonder if perhaps I could make good use of the inversion bug, using it to extinguish outputs without the usual extra circuitry required when input is out of range. I've read mixed reports on the TL06/07/08 series, LF356 & MC34081 so question is which cheap common opamps can I /rely/ on to invert outside of a narrow input voltage range? An opamp where V_in needs to go close to the