Precision Hub - All Comments

RE: Stress-induced outbursts: Microphonics in ceramic capacitors (Part 1)

John Kolchmeyer — Wed, 07 Jan 2026 21:59:09 GMT

What is the schematic of the circuit that generated the voltages shown in Figure 1 above? What is the volts/div of the Y axis in Figure 1?

RE: How to design current sensing and protection with off-the-shelf op amps

Dale Walsh — Wed, 02 Jul 2025 12:45:14 GMT

I'm looking for some assistance, I'm a hobbyist who knows enough to be dangerous and the issue I have is that my Vsupply is 140VDC and I'm trying to adjust the circuit to work with this supply.

I have adjusted R1/R3 (100K/4.5K) and R12/R13 (6.5K/100K), do I need to change the values of R2, R4, R5, R6, R7, R8, R11?

I also notice that R9 and R10 have no value, and I was thinking that this might be an issue since I'm driving an inverted complimentary transistor pair to drive the gates on quad parallled mosfets (share output load) so I was thinking 560R/1.5K would be sufficient.

I can't upload a picture so I'm not sure how to post a pic of my schematic.

RE: Introducing…your hub for analog precision design

Bruce roky — Fri, 21 Feb 2025 13:58:44 GMT

the Hub is great,we love it and help us much (bruce from supsemi)

RE: 2-wire 4-20mA transmitters: Controlling 2-Wire Transmitter Outputs with Externally Powered Sources (Part 4)

Faisal Bala — Sun, 29 Sep 2024 14:25:43 GMT

Hi, I am designing a 0-20v to 4-20mA signal converter for an electric pump. I can't find any reference design for this case.

RE: Understanding Voltage References: Using a Shunt Reference as a Comparator

Brian S. Hansen — Mon, 16 Oct 2023 09:20:18 GMT

What will be the voltage drop over the regulator when V_X > V_{TH ?}

RE: How to enable high-accuracy CW Doppler through discrete, precision data converters

Kuba Sunderland-Ober — Fri, 06 Oct 2023 00:39:15 GMT

It’s worth saying that Doppler measurements are amplitude-insensitive. The output signal is a frequency difference. The reference source for the ADC can be pretty lousy as long as it has low noise in the ADC bandwidth of interest. And even then, the contribution would be mainly to the SN ratio, not accuracy overall. In contrast with, say a DC absolute measurement, where reference voltage errors show up in the output.

RE: Zero out your system error with zero drift, zero crossover and zero hassle

Kuba Sunderland-Ober — Fri, 06 Oct 2023 00:32:41 GMT

Input crossover distortion is only a problem when the common mode is not held constant. Best performance from any op-amp, be it brand new design or decades old, usually requires the common mode to be constant. So, these op-amps solve a problem that doesn’t come up if the application design was done right to start with. Alas, sometimes non-inverting stages seem to be the “simplest” solution. And then the complexity shifts onto the IC op-amp designer :) If you don’t want to marry the design to this unique part, and don’t have a spare charge pump laying around, it’s best to make the whole thing insensitive to both CMRR and crossover distortion in one fell swoop.

RE: How to layout a PCB for an instrumentation amplifier

Kuba Sunderland-Ober — Fri, 06 Oct 2023 00:26:40 GMT

The resistance contribution from the traces between input series resistors and the shunt resistor is dwarfed by the mismatch between R1 and R2 just due to their tolerance. So, DC offset introduced by the input bias is solely due to R1-R2 imbalance. DC CMRR won’t be affected much.

however, AC CMRR suffers from any asymmetries on in amp inputs. The layout must be symmetrical from the input pins to the signal source. Parasitic capacitances to the ground plane must be balanced between inputs.

If symmetric layout is not possible due to space constraints, the non-symmetric layout has to be optimized by EM modeling and then careful measurements to ensure that parasitics from both inputs to adjacent copper fill are balanced. If EM modeling is not available, a test PCB has to be made with asymmetries stepped by say 1 mil of spacing, over several mils. That way the most balanced layout can be chosen by measurement only. Physical models beat numerical models every time as long as they are affordable. In this case, a small test PCB costs next to nothing.

RE: Delta-sigma ADC basics: Walking around the delta-sigma blocks

gvs t — Wed, 13 Sep 2023 08:04:57 GMT

can you share details about SD24_B output format configuration.

RE: Circuit-protection basics

Christopher Arena — Wed, 13 Sep 2023 03:18:51 GMT

A basic circuit protection measure would be protection from inductive spikes. Using the INA219 in a motor current measurement application, possibly using the DRV8871 as the motor driver, configured with protection would be an excellent example showcasing both parts and answering a real world problem with them.

Thanks,

Chris Arena

Jeffersonville, VT

RE: Circuit-protection basics

Christopher Arena — Wed, 13 Sep 2023 03:17:46 GMT

A basic circuit protection measure would be protection from inductive spikes. Using the INA219 in a motor current measure application, possibly using the DRV8871 as the motor driver configured with protection would be an excellent example showcasing both parts and answering a real world problem with them.

Thanks,

Chris Arena

Jeffersonville, VT

RE: And then there was noise: The mystery of the missing ENOB (Part 2)

Daniel Ka — Fri, 24 Feb 2023 09:43:50 GMT

The provided link to the final part does not work for me.

I found the final part here: 3rd part

RE: And then there was noise: The mystery of the missing ENOB

Daniel Ka — Fri, 24 Feb 2023 09:42:39 GMT

The provided link to the 2nd part of this story does not work for me.

But this link works: 2nd part

RE: ADC Accuracy Part 1: Is accuracy different from resolution?

Abhilash Naragund — Sat, 07 Jan 2023 20:40:17 GMT

Hello Everyone, I would like to ask you about the selection of resolution of ADC. Do you have any calculation to arrive at n- bit ADC? If so could you share the methodology please? I am working on the measurement of strain/stress/force calculations using Strain gauge sensor project. My idea of connecting: Strain gauge diagonal bridge (I have -0.49mV for maximum loading condition as an output from the strain gauge bridge) > Instrumentation Amplifier > ADC of high resolution so that it can accept the amplified analog voltage(Example:ADS1256) > WiFi enabled Microcontroller. Could you please guide me in this regard further? Your feedback will really helps me in proceeding further with my project. If further clarifications, I am happy to contact you over the Teams meeting. My mail ID: abhilash.naragund@student.uni-siegen.de

RE: Understanding Voltage References: Shunt vs series. Which topology is right for you?

Kai Zhou — Tue, 27 Dec 2022 01:18:50 GMT

why equations 1 and 2 is not belowed equations:

RS_MIN = (VIN_Max - VOUT) / ( ILoad_Max + IQ_Max)

RS_Max = (VIN_Min - VOUT) / (ILoad_Min + IQ_Min)