30 votes
Accepted

How to identify filter behaviour without memorizing different topologies

Look at the extremes. DC and very high frequencies. For DC you can remove the capacitors and short the inductors. For high frequencies you can short the capacitors and remove the inductors. By looking ...
Mario's user avatar
  • 8,195
20 votes

Why do we need R1 in a non-inverting op-amp?

It's for biasing the (+) input. If it's not there, then the bias current of the op-amp will have no where to go and the voltage at that node will drift. This RC combination forms a bit of a high-pass ...
Designalog's user avatar
  • 3,790
12 votes
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Design constraints when dealing with very high resistances in op-amp's feedback loop

I used to do condenser microphone stuff professionally, which was very much this kind of thing (10G ohms with maybe a 30pF source). Cleanliness is VITAL, a bit of skin oil in the wrong place and you ...
Dan Mills's user avatar
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12 votes

How to calculate values for decoupling capacitors

Basically you want something close enough to the pin that at the edge rates in play the bounce is not too bad, and then something further away with (possibly) enough ESR to damp everything to keep the ...
Dan Mills's user avatar
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10 votes
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What is the purpose of the 250uF capacitor in the LM386 circuit?

Yes, 470uF will work fine, it will just extend the bass response somewhat. It's a coupling capacitor (or a blocking capacitor, to block DC, if you prefer). The 10R + 50nF is a "Zobel Network", ...
Spehro Pefhany's user avatar
9 votes

Conundrum: High pass filter passes DC?

The resolution to the conundrum is that there really is no conundrum. Your input, a step function, has infinite dc component (its Laplace Transform, \$1/s\$, goes to infinity as \$s\rightarrow 0\$). ...
rpm2718's user avatar
  • 2,642
9 votes

Conundrum: High pass filter passes DC?

You're confusing the steady-state response with the total response. The transfer function for that circuit is: $$H(s)=\frac{s}{s+\frac{1}{RC}}$$ and if you solve for the step response: $$h(t)=\text{e}^...
a concerned citizen's user avatar
9 votes
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Will capacitor in high pass filter pass high frequencies while it is blocking low frequencies?

And at low frequencies and DC currents the cappacitor gets fully charged very early at the beginning of the cycle and acting afterward as an open circuit until the voltage drops in the second half ...
Neil_UK's user avatar
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9 votes
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Why do my high and low pass filters look like high pass filters in LTSpice plot?

Look what you have plotted in both graphs: - And, of course both circuits will have the same input current no matter which position the R and C are in. You need to plot Vout.
Andy aka's user avatar
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8 votes

High Pass vs Low Pass simple Circuit (RC vs CR)

For years I tutored the very first electrical engineering course at my uni, so this comes up a lot - don't worry :) The best way to understand this is to think about all 4 cases: An AC (or, you ...
DSWG's user avatar
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7 votes
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Questions about the Baxandall circuit

Your circuit is indeed a tone control circuit. For low signal frequency (Bass booster) we can ignore \$C_2\$ and \$C_1\$ because for low-frequency capacitance reactance \$X_C\$ is high. So we have ...
G36's user avatar
  • 14.5k
7 votes

How to calculate values for decoupling capacitors

tl; dr: it’s not just about the cap values, but their parasitics too. The data-driven technical answer is, you model it if you have access to the very expensive power integrity software that takes ...
hacktastical's user avatar
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7 votes

Why is the instrumentation amp distorting the signal on the input?

I believe the problem lies in the placement of just one wire in your schematic. Try this: I've kept the RC time constant the same, but chose somewhat differently for the resistor and capacitor values....
jonk's user avatar
  • 77.8k
7 votes

Why is the instrumentation amp distorting the signal on the input?

The bumps come from the current flowing into the output capacitor with those "real" 0.65 ohm resistances, and since you have coupled the inputs through the (-) power supply rather than ...
Spehro Pefhany's user avatar
7 votes
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Concatenating first-order high-pass filters

Cascaded 1st order filters, when buffered and with the same elements, converge towards a Gaussian bell. It only happens after many such stages, but that's the point of convergence. For your case, as ...
a concerned citizen's user avatar
7 votes
Accepted

Modulating a high-frequency signal to get rid of an undesired low-frequency component

For such measurements done with a sampling oscilloscope, the time base of the scope and of the function generator must be synchronized to a common reference. In a lab where you deal with precise ...
Kuba hasn't forgotten Monica's user avatar
7 votes
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What is this following filter circuit called? (For amplifiers)

The way the capacitors are currently drawn is a bit confusing, and reflects their physical wiring rather than their actual configuration. It is helpful to redraw the circuit slightly, so the two ...
nanofarad's user avatar
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6 votes
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What is the purpose of the series of actions: amplification, band-pass, rectification, and low-pass?

The signals from the sensors were tiny, and needed to be amplified. Otherwise they would be lost in the noise in the rest of the system. When "interesting" things happen, neurons fire rapidly. ...
Simon B's user avatar
  • 19.2k
6 votes

RC differentiator giving a higher output amplitude than input amplitude

It's called "charge pumping", and it is sometimes used to create low-power boosted-voltage supplies for some applications. At the end of each half-cycle, the capacitor is essentially charged to the ...
Dave Tweed's user avatar
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6 votes
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RC differentiator giving a higher output amplitude than input amplitude

Think of a capacitor as "liking to keep the voltage across it constant" - at least in the short term. Figure 1. Voltage difference analysis. Just prior to the squarewave step down at (1) we can see ...
Transistor's user avatar
  • 175k
6 votes

Why do we need R1 in a non-inverting op-amp?

Assuming ideal components, R1 works with C as a high-pass filter. Select R1's resistance such that \$f_{corner} = \frac{1}{2\pi{}R_1C}\$. Your microphone probably has a lower frequency limit; this is ...
Matt S's user avatar
  • 3,457
6 votes

Why do we need R1 in a non-inverting op-amp?

For a classic non-inverting opamp circuit, the action of negative feedback is to do whatever is necessary to drive the inverting input such that the voltage difference between the inverting and non-...
AnalogKid's user avatar
  • 19.6k
6 votes

Why do we need R1 in a non-inverting op-amp?

What is the purpose of putting R1 there? Two devices need R1 - the input circuit (because of the charging of the capacitor) and the op-amp (because of the input bias currents). There is no connection ...
Circuit fantasist's user avatar
6 votes
Accepted

What is the coil for in these cheap tweeters?

I'm going to draw the diagram differently, but the electronics is the same, Bryan's auto transformer is correct. The diagram is not different from glen_geek's diagram or the OP, just rearranged t ...
RussellH's user avatar
  • 14.7k
5 votes
Accepted

Will a resistor connected in parallel with a high-pass filter affect the filter cut-off freq?

The "trick" you lack may be using the superposition principle to "ignore" (temporarily) the DC source and consider it to be 0 V while studying only the AC source. Using the superposition principle, ...
MaximGi's user avatar
  • 1,041
5 votes
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Biasing an AC voltage for input to ADC

The ADC input floats to some DC voltage. If you disconnect your voltage divider from the ADC, you will see the voltage on the ADC float to some DC voltage. The ADC input looks something like this: ...
JRE's user avatar
  • 70.9k
5 votes

What is the purpose of the 250uF capacitor in the LM386 circuit?

Figure 1. Typical LM386 amplifier circuit. For an audio application driving a loudspeaker alternating voltages must be generated. A positive voltage on the output drives the speaker cone one ...
Transistor's user avatar
  • 175k
5 votes
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High pass filter - Cut-off frequency calculation doesn't match simulation

From the simulation, it looks like it fc=500Hz or somewhere around there. Your simulation looks more like 15 kHz (3 dB point) and the reason is because you haven't used enough resolution in your AC ...
Andy aka's user avatar
  • 452k
5 votes

High pass filter - Cut-off frequency calculation doesn't match simulation

Well, mathematically speaking we can write: $$\mathcal{H}\left(\text{s}\right)=\frac{\text{sL}}{\text{sL}+\text{R}}\tag1$$ Using \$\text{s}=\text{j}\omega\$, we get: $$\left|\underline{\mathcal{H}}\...
Jan Eerland's user avatar
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