Analog Top Talks in June 2019 on EDABoard.com

Peer-to-peer, engineer-to-engineer questions and answers from the EDABoard.com engineering community around analog ICs and analog design. Click the “Read more” link and follow the entire conversation and maybe add your two cents by logging in to EDAboard.com.

Pulse width stretching – I want to design a circuit for stretching the “0” output of my signal. I have seen the Monostable multivibrator but it stretches the “1” output. is there anyway flipping it or another topology for realizing that? Read more

Pulse charging capacitor through diode – I am trying to pulse charge a few capacitors through diodes, here is the schematic below. Q3 and Q4 are both OFF in this test. C6 is the problem area. Read more

Half-bridge 0-30V, 0-20A feedback loop problem – Plans to design an adjustable power supply based on the SG3525 controller with the possibility of voltage regulation ~ 0-30V and current ~ 0-20A. I have a working power stage, which is able to give over 20A at 30V, while I have a problem with the implementation of the feedback loop. I use an external LM324 operational amplifier which realizes two feedback loops -—voltage and current. Read more

TL431 temperature compensation method – I can’t re-create 0ºC to 100ºC here at home nor have appropriate tools to measure the effects on the DUT anyway. Question: Does the simulation result “B” look credible? I possibly more or less understand the premise of what the diodes do but no idea why it turns the expected “banana” into a “sideways s” either. Diode leakage increases with temperature and draws current away from ref pin, which internally in the TL431 is an NPN base. Read more

TDA2030 amplifies noise – I recently made a 12v single supply tda2030 amp and it’s very noisy. All non-polarized caps are 0805 or 1206 MLCCs the board has a footprint for 4700uF rail capacitor instead of 220uF – haven’t tried 4700uF but circuit with 220uF made noise lots of noise with 2.3R and 8R speakers powered by a Meanwell GST60A12-P1J 12v 5A adapter. What can be done to remedy the noise issue? Read more

Shortcircuit protection circuit – I need a fast and simple short-circuit(or Over-voltage) protection circuit. My input voltage is 24V and max output current is 2A. How can I protect my power supply from over-current?
I need the simplest and reliable circuit. Read more

Using a potentiometer to measure arcseconds – How should I pick the correct type of potentiometer that will measure an angle to the nearest arcsecond (.000278 degrees)? What parameters and their values for a potentiometer would be important to consider for this kind of application? Read more

NPN is behaving as oscillator – We have a DALI communication setup. To be brief, DALI is basically square wave transmissions at 1200Hz. A DALI bus is pulled down and released at the 1200Hz frequency, as in the attached schematic. (LTspice sim also attached) In our DALI circuit, the node RA3 is following the transmission of the DALI bus, and is obviously an inverted form of it…however, within the high-going pulses at RA3, there is an approximately 120kHz oscillation….which is rendering the comms not working. Read more

Adding a pulsed switch to a DC voltage source in Cadence library – I want to add a switch for creating a pulsed output with a certain frequency. I know that the voltage source could be pulsed but I need to keep it on a certain dc voltage and the switch will just have to follow this voltage. does anyone have an idea which component in cadence lib would achieve that? Read more

XOR gate IC supply current – I  have a circuit that I need to use XOR gate IC using battery power. The chip in question is 74HC86. As per the datasheet, the supply current should be between 20 to 40 micro amp, but, if I just power up the chip using Vcc and ground, it is using 3 to 7ma of power. Read more