Analog Top Talks in January 2019 on EDABoard.com forums

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.

How to design a thermostat without microcontroller – I want to have an electronic thermostat when the temperature reaches to 37 °C turn a relay Off. Do you have a circuit? Read more

OP amp output oscillating – When input voltage gets to 47mVon the LM358P OP AMP U1:A strengthens that voltage by 48 times and OP AMP U1:B compares it against reference voltage 2.18V and turns on output to PIC digital input. I get around 3.75V to the pic input pin. According to PIC12F683 datasheet min 2.0V needed to recognize it as HIGH state. So that is ok and it actually works just fine on breadboard. However, I decided to change the OP AMP to LM2902N and ended up in trouble.  Read more

How to create negative voltage -700mV – I need to create negative voltage -700 – -1000mV max current 30mA (typical 5mA) from positive +5 or +3,3V. Read more

DC sweep convergence issue for CMOS inverter – I am having some convergence issue with DC sweep for a CMOS inverter. To duplicate the exact issue, see the log as well as the attached netlist files, together with modelcard.nmos and modelcard.pmos. I have tried various suggestions online (such as bypassing .op analysis , using smaller dc sweep step, use .ic initial condition, add parasitic resistance to circuit nodes), but those do not help in my case. Read more

Weathering the 0603 shortage, and designing for 0402 and 0201 – I am in a supporting role for a project to redesign some PCBs to use 0402 and 0201 package sizes, instead of the 0603. What are some of the most important component specifications to take into consideration when making a design change like this? Read more

Some questions about common drain amplifier – I have some questions about common drain amplifiers. Common drain is known as source follower/voltage buffer. But in a large signal, I thought the highest output it could only be Vin – vth. Why it is called as voltage buffer or source follower since it should won’t reach the level of Vin? Read more

RTD temperature measurement with 5V ADC – I want to design an RTD based temperature transmitter with a 5V ADC. I do not intend to use a lookup table though. I’ll implement the reading with a formula so that won’t be a problem. I just want to know the conventional way of doing it. I know I can just measure the voltage and infer. Read more

Zero AC gain of CMOS inverter – Why does the following AC analysis of CMOS inverter result in zero AC gain (vout/vin)? Read more

LTC 4015 IC fails when used for separate charge and discharge path – I did an experiment on LTC4015 IC for battery charging and discharging. As per datasheet typical application circuit, Verified Vin and battery charging and discharging. It’s working fine. When turn ON and OFF the LTC4015 SYS terminal output(J2 connector), LTC4015 get damaged. Read more

Long OFF_time timer by 555 –  I want to have a timer where the OFF time of the output should be 1 hour and ON time to be 10 sec. It should be implemented by IC 555. Read more