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Type: Posts; User: crutschow

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1. ## Thread: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

by crutschow
Replies
2
Views
231

### Closed: Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

Sampling bandwidth is defined by the Nyquist criteria, i.e. the sampling frequency must be greater than twice the highest signal frequency of interest to reconstruct the waveform (in practice a...
2. ## Thread: Full wave bridge rectifier but doing half wave

by crutschow
Replies
10
Views
681

### Closed: Re: Full wave bridge rectifier but doing half wave

Unless you got an autotransformer, the primary and secondary of a transformer are isolated.

And I don't see how AC main's grounds can be "isolated".
By definition all AC grounds go to earth.
3. ## Thread: Full wave bridge rectifier but doing half wave

by crutschow
Replies
10
Views
681

### Closed: Re: Full wave bridge rectifier but doing half wave

Yes.
And adjust both inputs to have identical gain.
You can check that by connecting both inputs to the same signal (such as the AC voltage) and adjusting for the minimum displayed voltage.
4. ## Thread: Full wave bridge rectifier but doing half wave

by crutschow
Replies
10
Views
681

### Closed: Re: Full wave bridge rectifier but doing half wave

Yes, it's a common mistake for newbies to connect the input and output of a bridge circuit to a common ground, which will not work.
It you look at the current path, you will see why.
5. ## Thread: how does a coaxial cable work?

by crutschow
Replies
5
Views
421

### Closed: Re: how does a coaxial cable work?

The forward signal current is carried by the inner conductor and the return signal current by the outer conductor, but the outer conductor us typically maintained at ground potential at both ends of...
6. ## Thread: impedance of antenna

by crutschow
Replies
16
Views
809

### Closed: Re: impedance of antenna

The impedance of the antenna (ignoring any parasitic losses) is its radiation resistance to free space, and is determined by the physical/geometric design of the antenna and the frequency.
Some...

by crutschow
Replies
3
Views
352

### Closed: Re: Overvoltage Protection

You have no DC supply connection to the transistor emitter, so it won't work.
8. ## Thread: Ultra low-power timer to make a power saving circuit

by crutschow
Replies
24
Views
1,477

### [SOLVED]Closed: Re: Ultra low-power timer to make a power saving circuit

Here's a reference for a CD4060 circuit that will give up to a 24-hour delay.
If you omit the transistor, LEDs, and relay, the average current draw should be only a few microamps.
That could likely...
9. ## Thread: solution to over current / protection circuit

by crutschow
Replies
9
Views
626

### [SOLVED]Closed: Re: solution to over current / protection circuit

The inhibit signal is then low, so a power loss from the ucontroller will turn off the motor board (adding a pull-down...
10. ## Thread: Power Supply Design for timer application

by crutschow
Replies
10
Views
795

### Closed: Re: Power Supply Design for timer application

Delete the 7805 and use the common 5V wallwort.
They are cheap and provide isolation from the mains.
11. ## Thread: How to find Vec of an active mode pnp

by crutschow
Replies
3
Views
314

### Closed: Re: How to find Vec of an active mode pnp

It that's a simulation, just run a transient simulation and plot the voltage at that node.
12. ## Thread: Accurate mains zero cross detector circuit without optocoupler

by crutschow
Replies
14
Views
1,032

### Closed: Re: Accurate mains zero cross detector circuit without optocoupler

Why do you call that a "wear-out" component?
Provided they are used well within their ratings, opto-couplers are just as reliable and long-lasting as most other solid-state devices.
13. ## Thread: Ramping a reference voltage up from, or down to zero volts, over ~200us

by crutschow
Replies
9
Views
887

### Closed: Re: Ramping a reference voltage up from, or down to zero volts, over ~200us

Below is the simulation of a example circuit using 4 resistors in a binary ladder network to give the 16 steps.
It is shown connected to the 5V outputs of a binary counter (outputs 1, 2, 3, and 4),...
14. ## Thread: Ramping a reference voltage up from, or down to zero volts, over ~200us

by crutschow
Replies
9
Views
887

### Closed: Re: Ramping a reference voltage up from, or down to zero volts, over ~200us

Can you use a microcontroller with a DAC output (not PWM)?
Or use an external DAC?
Or, if you have four spare digital outputs on the micro, you could use a simple 4-resistor ladder network with an...
15. ## Thread: Discrete transistor voltage regulator

by crutschow
Replies
19
Views
1,676

### Closed: Re: Discrete transistor voltage regulator

Just use a LM317 regulator with one 120 ohm resistor and one 500 ohm pot (plus a couple decoupling caps).
That will allow adjustment of the output from 1.25V (the stable internal reference voltage)...
16. ## Thread: Discrete transistor voltage regulator

by crutschow
Replies
19
Views
1,676

### Closed: Re: Discrete transistor voltage regulator

Is that AC or DC?

Making a simple discrete regulator whose output can go below its reference voltage is problematic, unless you use an op amp.
17. ## Thread: Discrete transistor voltage regulator

by crutschow
Replies
19
Views
1,676

### Closed: Re: Discrete transistor voltage regulator

That circuit uses the base-emitter voltage of Q1 and the forward diode drop of D1 as a voltage reference, so the minimum output voltage would be about 1.3V.
If you eliminated D1 and connected the...
18. ## Thread: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

by crutschow
Replies
13
Views
1,082

### Closed: Re: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

The simplest is just to use an RC delay with a Schmitt-trigger input, such as a CD40106, and tweak the value of the resistor to get the desired value, if needed.
LTspice simulation below:
There is...
19. ## Thread: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

by crutschow
Replies
13
Views
1,082

### Closed: Re: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

Do you have a digital clock signal available?
20. ## Thread: Analog realization of trignometric function

by crutschow
Replies
8
Views
1,148

### Closed: Re: Analog realization of trignometric function

Here's a way to approximate the sine function using an analog multiplier (from this paper.).

156906

by crutschow
Replies
36
Views
1,509

### [SOLVED]Closed: Re: Average vs RMS load-current for LDO design

A significant point missed is that RMS current only works as an indication of power with a resistive load.
For a constant voltage load, such as a switching power supply, the average current is the...

by crutschow
Replies
36
Views
1,509

### [SOLVED]Closed: Re: Average vs RMS load-current for LDO design

As I stated, for a steady DC output, such as from a linear regulator, the average current is the same as the RMS current (for DC the RMS calculation is trivial).

by crutschow
Replies
36
Views
1,509

### [SOLVED]Closed: Re: Average vs RMS load-current for LDO design

For a DC current, the average and the RMS are the same.
24. ## Thread: Determining output impedance in LT SPICE

by crutschow
Replies
7
Views
701

### Closed: Re: Determining output impedance in LT SPICE

Well, commonly when the term transistor is used without any further information, BJTs are being referred to.
So you'll have to pardon me If I didn't realize you were referring to MOSFETs.
25. ## Thread: Determining output impedance in LT SPICE

by crutschow
Replies
7
Views
701

### Closed: Re: Determining output impedance in LT SPICE

For gm, you can vary Ib and do waveform arithmetic of Ic/Vbe (right-click on the waveform title).

For output impedance, you can vary the collector voltage and do waveform arithmetic of Vce/Ic for...
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