Analog Top Talks in December 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.

Signal integrity problem in a 100MHZ CLK –  I am wondering about a signal integrity issue with a 100MHz clock generated by an FPGA. This is the set up:
– FPGA generates a 100MHZ square signal with 50% of duty cycle.
– The IO constraint is LVCMOS 3.3V.
– The PCB track has a length of 20cm, and it finished in a Sub-D25 connector. The track has a series termination resistor (Rt). Read more

P-mos not turning off – The p-mos(U1) remains OFF initially when n-mos(Q1) is OFF. Once, a signal from n-mos(Q1) is sent, the p-mos(U1) turns ON, but, even after turning OFF the n-mos(Q1), p-mos(U1) remains ON. Can anyone tell me the reason? Read more

 

Tuning of transconductance in OTA circuit – I want to tune the transconductance of OTA. For transconductance tuning I have to vary the biasing current. But how can I vary the biasing current what circuitry should be used to vary the biasing current for transconductance tuning. Read more

PLL and DLL and their differences?  – I want to become intimate with the PLLs and DLLs. I think the best way is to design and operate them in simulation and on bench. However, I am not sure where to start. It is possible to create them in MATLAB Simunlink (maybe) to learn about how the mechanism works. But I don’t know if they can be constructed using different components on bench or can only work in an integrated circuit. Read more

Workaround for power supply not local with receiver input – I’m stuck with an issue. A 0 – 5V 33Hz pulse train needs to be interfaced with an optocoupler 4N46 before it reaches to a DAQ input. This needs to block common mode EMI which introduces noise at this DAQ‘s input. Read more

Folded cascode amplifier is an op-amp or OTA? – I want to know if a folded cascode amplifier is an OTA or opamp. Read more

Distorted sine output from transformer – I am using an amplifier (LT1210) with +-15V supply and its output is connected to a transformer RM10 core N97 with 9:150 step-up ratio and its output has to be connected to various piezoelectric transducers in the range 40 to 300 kHz and impedances varying from 20 to 2.5kΩ. The problem is I can’t amplify my signal as much as I want to as the sine wave gets distorted and also I have to connect a resistor between amplifier and transformer to make this circuit work. Read more

Slew rate and slew rate limiting –  If the value of the maximum change of the output of the opamp is greater than the slew rates positive and negative (single-ended output) – then I don’t get slew rate limiting OR is it less than the positive and negative slew rates? Read more

5-decade precision current sense application – I’m concepting a current sense application covering about 5 decades from 500μ to 5A where high precision <0.1% AC/DC and high bandwidth ~1Mhz are required (high precision applies to <<1mhz). Ultimately the signal is fed to an ADC (>5MSPS). So first I think it’s obvious this requires multiple shunts and my thought is to space them every decade -> 0.01/0.1/1/10/100.  Read more

Arduino controlled light dimmer – Working on an urgent project of a light dimmer that starts low and the gets brighter in 4 steps — 5% glow then 20% then 50% then 80% or even gradually still good. I found the circuit below at this great website. The light power I need is 3000 W. Can I simply replace the Triac with a bigger power like BTA41-600V? Or do I need to make other changes on the circuit? Read more