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Posts by TonyStewart‭

42 posts
71%
+3 −0
Q&A Using FET based followers and design rules

Allow me to address the MOSFET only as a source follower. this has very unpredictable linear use without voltage = current feedback as the RdsOn at threshold has a wide tolerance.(>20%) (Many...

posted 3y ago by TonyStewart‭  ·  edited 3y ago by TonyStewart‭

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Q&A Capacitor ESR vs. Impedance

Capacitors are lossless with 0 ESR and rise in temperature and become less reliable by 50% for every 10’C rise due to I^2ESR=Pd losses. However the current spectrum must be known with the ESR frequ...

posted 3y ago by TonyStewart‭  ·  edited 3y ago by TonyStewart‭

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Q&A Circuit which create ac sine wave from dc pulsed signal

This is about as simple an analog inverter that I can simulate, but warning, not for the beginner with resonance issues. The bridge diodes are 2f multipliers reduced to logic level with divide by ...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A How to plot the I-V curve of a tunnel diode?

How to test a Tunnel diode in 25 words or less. With DC bias = ~490mV with fine tuning and a small signal swing of 60mV you can generate a IV negative slope of -16 Ohms.

posted 3y ago by TonyStewart‭  ·  edited 3y ago by TonyStewart‭

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Q&A Ceramic capacitor "memory" effect?

I have never seen this slow drift in ceramic caps, yet I have seen fast memory effect drift in S&H designs using high Dk ceramic capacitors in the 70's. So I have learnt that all ceramic caps h...

posted 5mo ago by TonyStewart‭

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Q&A Testing instrumentation amplifier with differential signal

It is important to realize that an ECG signal is high impedance and this easily picks up line voltage E-fields. Using a 50 Ohm sig.gen. is a poor simulation of the use of this circuit and also neg...

posted 1y ago by TonyStewart‭

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Q&A What is the difference between rise/fall time and Turn-On/off Delay Time?

To understand the timing, you must understand the cause. Delay is the time from input to output It is measured from +10% of input to 90% of output ( or a 10% change in output), unlike logic chips ...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A Ceramic filter vs ceramic resonator

A resonator cannot replace a filter because the filter has multiple resonances to extend the bandwidth. For AM carrier modulation using a narrow band resonator with 0.5% tolerance of 6MHz or +/-30...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A pH Electrode Buffer - Offset when solution grounded

DC offsets in hundreds of mV from different grounds may be coming from either the floating ground or the PE earth. The latter may be from rectified AC line filter noise shunted to PE. The former m...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A When do I need to put anti-aliasing filter in front of SAR ADC?

Anti-Aliasing filter depends on the following parameters; Signal BW Sampling Rate Sampling duration and thus BW of sample LPF attenuation of alias spectrum above 1. From your SNR spec or dy...

posted 2y ago by TonyStewart‭  ·  edited 2y ago by TonyStewart‭

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Q&A Design high -pass filter with 2 points of the bode plot

Filter design 101 given hypothetical high-pass (HPF) filter -3dB gain HPF at fc attenuation of -8dB at fc/2 Assumptions gain = 0 dB at f>> fc Ripple between -3dB and 0 dB...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A Low-pass filter after the output DAC in CD players

The oversampling is said to simplify the LPF yet the better reason is that it improves the SNR. Lower noise comes from better image rejection, lower filter ringing, and significantly lower group d...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A What reactance actually is?

Reactance is the lossless part of impedance that stores and releases energy E=1/2 LI^2 or 1/2CV^2 . Much like a spring stores energy when compressed or expanded. L is a conductor that stores curr...

posted 2y ago by TonyStewart‭

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Q&A Why are antenna PCB traces square instead of rounded?

Corners and chambers that are a small fraction of a wavelength are not significant in the <4Ghz band. More significant is the tolerance and loss tangent on the substrate. They would hardly be m...

posted 3y ago by TonyStewart‭  ·  edited 3y ago by TonyStewart‭

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Q&A What does it mean for a signal to have impedance?

$$Z = R + jX $$R is a real resistance that stores energy as heat and temperature rise which depends on the thermodynamic property of thermal resistance which is impacted by an enclosure to get hott...

posted 1y ago by TonyStewart‭  ·  edited 1y ago by TonyStewart‭

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Q&A Why arc welding does not require high voltage to arc?

gas tubes, SCRs, and welder arcs all have negative incremental resistance. This means when conduction begins, the resistance drops like a crowbar and is sustained until the current drops belo...

posted 1y ago by TonyStewart‭

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Q&A what should the output be for this use case of the CD4047 chip?

Possibly it is damaged. Be ESD aware and do not power up with any voltage on any pins > 0.5V (Latchup failure) If raising p9 (reset) does not lower Q to logic "0"=<20% Vdd) replace the ...

posted 11mo ago by TonyStewart‭  ·  edited 11mo ago by TonyStewart‭

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Q&A How is it possible to perform a open circuit test on a induction motor?

~ In an open circuit test, also known as a no-load test, an induction motor is operated without any mechanical load connected to its shaft. The purpose of this test is to determine the no-load loss...

posted 11mo ago by TonyStewart‭  ·  edited 11mo ago by TonyStewart‭

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Q&A Can the corner frequency of thermal noise change with change in source impedance?

Any time you have a dielectric interface ( ___ pF ) source resistance will always have an error in signal response until the electrode impedance is eqal or less than the sub-cutaneous impedance. T...

posted 8mo ago by TonyStewart‭  ·  edited 8mo ago by TonyStewart‭

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Q&A Essential safety features of an EMG/medical grade device?

Current limiting input differential Rs of 1M into a 10M INA with clamp diodes make this a simple task.

posted 8mo ago by TonyStewart‭

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Q&A What is Ground Electrode in EMG?

CMRR design is key to rejecting grid e-fields that impose noise onto EMG, EKG,EEG amplifiers. This includes all series Zs of cable balance and Amp CMRR. For this reason >100 dB CMRR are requ...

posted 8mo ago by TonyStewart‭  ·  edited 8mo ago by TonyStewart‭

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Q&A Estimating the input capacitance of an BLDC motor controller

To answer some of your questions: Cable inductance: approx 1uH/m +/-50% depends slightly on l/d ratio , while cable impedance from sqrt(L/C) depends on twists/ft 50pF/m while coax is ~100pF/m ...

posted 3y ago by TonyStewart‭  ·  edited 3y ago by TonyStewart‭

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Q&A CAN BUS monitoring with a LED

You'll need a differential comparator, something like what was suggested in here. But I'd look for a proper Canbus Rx and extract that to convert to single ended one shot to pulse for activity.

posted 4mo ago by TonyStewart‭

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Q&A What type of button is this on a remote control

It is interesting to see how they deposited these carbon electrodes over solder mask and copper traces both under the button foil switches and membrane switches alike which offer more tactile feel....

posted 3mo ago by TonyStewart‭  ·  edited 3mo ago by TonyStewart‭

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Q&A Control logic for mosfet in piezoelectric energy harvesting circuit

Every real part has resistance including your piezo current source. Every switch resistance is a loss in energy (I^2 R * t)=E and includes diode and transistor switches. What you need, I think, is...

posted 5d ago by TonyStewart‭

Answer