Analog Top Talks in October on EDABoard.com forums

(editor’s note: Intrigued by the problem? Have a question or another solution? Then click the “Read more” link and follow the conversation on EDAboard.com or log in to EDAboard and participate in the analog forum threads.)

Why the door ring can’t work? – I want to spend some time with my son so we decided to make a door ring. We bought a raw PCB and mated RLC. Unfortunately, after we soldered all the components on the PCB, the door ring can’t work. Attachments are TX, RX, and one ppt for soldering the components respectively. Read more

How to reduce complicated RC network – I am trying to determine the time constant for the following circuit: V is a DC voltage source. It is 0V at t<0. At t=0 it goes to voltage V. Cs is a sampling cap. I am interested in the time constant at Vout. I’m a bit unsure whether I can treat this is a DC problem since I’m interested in the charge time which is inherently a non-constant signal. Read more

Differential loss cadence – I was doing S-parameter simulation in cadence to find out the differential loss of a simple circuit. I know the simple formula for return loss Return Loss = (ZL-ZS)/(ZL+ZS). For simple resistor circuits, the hand calculation and the cadence simulation results are same. For the attached circuit I couldn’t able to realize the capacitors and find the return loss. In the following circuit, cap value= 2pF and resistances are 50 Ohms each with 100 ohm Port across them.I am getting a value of S11 = 299.717mV. But I couldn’t get the same value through calculation. Read more

Ambient light noise (sunlight & Fluorescent lamps) in photodetector – I am trying to estimate the shot-noise from ambient light sources (sunlight and Fluorescent lamps).
I expect to shield my photodiode as good as possible – so no direct light is hitting it.
Second, what is the relationship between photodiode area size and noise from ambient light – is it proportional like: Id(shot-current) = Area*responsivity*irradiance. Read more

Circuit biasing problem – How do I  bias this circuit correctly? Read more

DC motor simulation using equivalent circuit – I am working on a hardware project which simulates a DC motor, that is, a hardware circuit replaces a DC motor and performs the function of DC motor. When I realize the back emf circuit, I am not sure how to design it, so that it can with stand 40 A of load current. Read more

Learning how to do DC and AC operating point – I am trying to learn how to do proper DC and AC operating point biasing for a simple transistor amplifier circuitry. Could anyone guide me? Read more

Need help with FM transmitter – How can I make a coil of the same value of the inductor in this transmitter circuit and what type of antenna is used? Will it be different if it is at a higher frequency? Read more

How to plot transconductance Vs Vid (differential) – I have an OTA with differential input and fully differential output. How can I see the correct Gm curve of OTA Vs differential input voltage? I want a simulation like these images. Read more

Speakers 16 ohms, 8 ohms, what’s the catch? – I bought this amp. It uses a PAM8406. Is it ok if I don’t use a speaker in perfect accordance to the amp specs? what is the risk ? Read more