# Tag Info

### How does an emitter follower work as an AM detector?

With no input signal, the bias network sets the base voltage to be about 3.4V. The emitter voltage is set to around 2.8V (depending on temperature) from a small amount of current coming from the ...
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### How are RF filters constructed?

As you've discovered, once you are up in the 100MHz+ range, little is "simple". When using discrete capacitors and inductors, you have to consider their parasitic complements. Even basic ...

### How can I calculate the total impedance of a second-order low-pass filter?

I have looked at this quickly, applying the fast analytical techniques or FACTs as described in my book on the subject. You first start by determining the input resistance for $s=0$: open the cap ...
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### How can I clip a voltage upper limit in an analog signal?

Many ICs have input protection diodes that will become conductive when the input falls outside the bounds of the power supply potentials (one or the other diode becomes forward biased), having a ...
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### Trouble with filter using Laplace transfer function in LTSpice

Save some grief: set $\omega=1$ Just save yourself some algebra grief and set $\omega=1$ when focused on a particular filter shape (like Bessel.) The filter shape can be moved around freely (at ...
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### USB 2.0 VBUS Filter

Letters and Decimal Points What does 5V0 mean? I've seen this net name used in other USB circuit diagrams (figure 1 here for example). Is 5V0 a convention used to indicate something different from ...

### What is the purpose of the resistor in a RC circuit?

simulate this circuit – Schematic created using CircuitLab Figure 1. (a) All pass. (b) High pass. I understand that a capacitor can pass high frequencies and block low frequencies, because of ...

### How can I clip a voltage upper limit in an analog signal?

Usually, when a very low level ANALOG input signal is to expected, a resistor is placed in series with the input, with a diode in parallel, like this: simulate this circuit – Schematic created ...

### How does an emitter follower work as an AM detector?

You are correct that if the emitter follower were employed as a linear element, it would be unable to perform AM demodulation. However, it is not as linear as you think. This NPN emitter follower has ...

### How to find the Transfer Function of this circuit?

You can easily determine the transfer function of this circuit by considering a simple $RC$ low-pass filter followed by a non-inverting structure described in this Wikipedia link. Because the op-amp ...

### Opamp Non inverting Input

Although an ideal op-amp will have zero input currents, a real op-amp will always have some current, called the input bias current on data sheets. For CMOS and other FET amplifiers, it can be very ...

### Input filter LC for switching power supplies

That's probably fine. A complete analysis requires much more information (voltage range, amount of ripple and noise, surge conditions if applicable, environmental, etc.), but these data likely don't ...
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### Input filter transfer function derivation

If you want to derive the transfer function linking the current signature of the buck converter to the current going to the battery, you don't need to include the battery voltage in the calculation: ...
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### Input filter to reduce conducted emissions caused by DC/DC converter

Everything starts with the current signature of the dc-dc converter fed by the EMI filter. For instance, you simulate your converter at steady-state and extract the input current. If the EMI filter is ...
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### Simulating a tuning circuit in LTspice

You have made a low Q or wideband filter. Increase R1 to sharpen it up. Try 10K then 100K.

### Simulating a tuning circuit in LTspice

Well, let's analyze this circuit. The transfer function is given by: \begin{equation} \begin{split} \mathscr{H}\left(\text{s}\right)&=\frac{\text{V}_\text{o}\left(\text{s}\right)}{\text{V}_\text{i}...

### How does an emitter follower work as an AM detector?

AM modulation is basically to multiply the carrier (C) and message (M) signals. And the result is, simply, the carrier signal "enframed" by the message signal: Above shows a 1 kHz signal (...
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### How to improve the performance of my low pass filter design

The LMH6626 is not unity gain stable!

### How to reduce oscillations in this active filter circuit?

Sallen-Key is the topology, Gaussian is the name of the filter design. Just to be clear, Gaussian filters are non-causal by design, which is why the filters that you'll meet in the wild are ...

### RLC band-pass filter

Your simulation is only running between 100 KHz and 10 MHz. Try editing the command to: .ac dec 1000 10 100K
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### Ripple rejection of capacitance multiplier when compared to linear regulators

1 - Why the Capacitance Multiplier has a better response ‘filtering’ the higher frequencies The very low quiescent current of the MCP1700 suggests that $gain \times bandwidth$ product is not ...

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### unfamiliar notch filter configuration

This is one of those interesting circuits. The upper amplfier, U1, is a differential amplifier. When redrawn, as below, the differential amplifier topology becomes clear. The Lower amplfier, U2, is a ...

### General formula for the ripple voltage in a loaded bridge rectifier

What is the general formula to calculate the peak to peak ripple voltage and Vdc average of the voltage at the input of the 7805 voltage regulator in a circuit like this? The general formula should ...