Analog Top Talks in January 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.

Flyback diode: it has one job, but mine…? – Please have a look at my simple circuit:

And here is the scope shot, as you can see, not working at all with 20V spikes building up, I would expect the diode to remove all/most spikes:

And here is a closer view

What do I do? How do I make the diode work? The problem is the same is I use SB220 or 1N4148 or PMEG2020 (Ultra Fast 20V 2A). Read more

5th order discrete-time Sigma-Delta modulator – I am designing a 5th Order Sigma-Delta Modulator – Discrete Time, with Single Bit Quantization. I am following the procedures of: Understanding Delta-Sigma Data Converters by Temes. In the text, they have an example of 5th order modulator with the following schematic. My question is in regards to capacitor selection. How does one go about selecting and sizing the capacitors in this 5th order discrete time delta sigma modulator? Read more

IC8038 – can this work – I’m planning to make inverter by using IC8038. It generates a sine wave signal. Can this circuit work? Read more

What’s the role of this NMOS? – I am designing a circuit shown in the picture below. In this circuit, there have a NMOS whose name is NM0. I don’t understand what’s the role of it. In fact, this circuit is a power supply and produces a 1V voltage to a DLL (delay phase lock). How can I understand the NMOS NM0? What’s the role of it? Read more

AC versus DC question – I am having some difficulty understanding the difference or the ‘actual distinction’ between fluctuating dc current and ac current, say with a microphone input into a small audio amplifier. Both are sinusoidal, but ac appears to regularly reverse it’s direction or polarity (+ to -) while dc appears to merely vary its voltage potential from a position of more positive to one of less positive. Read more

DC electronic loads with digital control? – It is not a problem to design and build an electronic load as HP 6060B, but it will be complex and complicated analog design. To solve this 4-channel load would be extremely expensive and complex. I’m thinking about hardware simple design…Read more

Evaluating open loop gain in a power amplifier – I have designed an amplifier with 133dB of open loop gain. Is too high? The question: more open loop gain means more stability? I have to reduce it? Read more

Type III compensation – I am beginning to think that PID control or any feedback control of power electronics converters is just magic and can only be performed by magicians. I have tried as a last attempt Type III compensation (PID) but the op-amp output is still saturated at Vcc.

I followed all the formulas given in the TB417 datasheet. Read more

ADC resolution & accuracy – I have read a sentence but can not understand it. The sentence is this A 2-bit ADC with 10-bit accuracy” in Understanding Pipelined ADCs. Read more

Beware of fake amplifiers on eBay using THS3091/5 part – Beware of fake amplifiers on eBay using THS3091/5 part. I am very aware of fake/cloned parts used by manufacturers, but decided to get the module as the part can always be replaced with a proper Texas Instruments part. Well, a few days ago, the module arrived from China, and I performed some basic tests on it in the lab.
1) It failed miserably to drive a 50 Ω load. While the open-circuit voltage could reach in excess of 20 Vpp, the loaded voltage with minimal distortion, was only about 5.6 Vpp!
2) Next I performed a bandwidth test and found it to be about 40 MHz, instead of the claimed 210 MHz. Read more