# Tag Info

## Hot answers tagged amplifier

### Why should the Vce be half the value of the supply source?

I don't know what you mean by: I know that such a thing is not usually valid in amplifier circuits You don't explain how you know this, or provide an example, so I can't comment on that. But you are ...
• 39k

### LTSpice simulation produced different results of phase margin when using step-signal % overshoot technique vs loop analysis technique

I spent some time with this and can now provide a better answer. I will leave the existing discussion for comparison. In the video by LT, the first attempt to stabilize the capacitive load was a ...
• 17k

### Why should the Vce be half the value of the supply source?

The quiescent (or average) value of $V_{CE}$ is usually chosen to be half the rail voltage. This allows AC voltages to sit at the mid-rail and be permitted to rise without asymmetrical clipping.
• 465k

### Is it correct to apply KVL through the 2 inputs of an op amp?

Negative feedback causes the op-amp to adjust its output potential to whatever is necessary to equalise its two input potentials. That's the principle behind the "virtual ground" you read ...
• 39k
Accepted

### Why does this transistor amplifier fail if Rc is greater than 50 ohms?

I wonder about accurate simulation of RF, using your current understanding of bipolar circuits. But I'll drop that and move on. A couple of bad things done in that ...
• 11.2k
Accepted

### Please explain the purpose of R3 and R4 in this ground isolating amplifier

Please explain the purpose of R3 and R4 in this ground isolating amplifier It boils down to recognizing that a differential amplifier using an op-amp has to use R3 and R4 (with the correct values) to ...
• 465k

### 50 Hz 2.5 Vpk-pk signal amplification

You have a 2.5 Vpk-pk signal, that's 1.25 Vpk. Amplify that by 10 (20 dB) and you've got 12.5 Vpk or 8.84 Vrms. Into 22Ω that's 3.55 Wrms. Peak current will be 568 mA. So you need an amplifier that ...
• 25.1k
Accepted

### Please help me identify this IC - top marking "CEK"?

Most probably it is a single 2-input AND gate, SN74LVC1G08DCK in SC70 packaging.
• 1,226

### Is it correct to apply KVL through the 2 inputs of an op amp?

It's not KVL that makes the voltages across each pair of differential inputs zero, it's an effect of negative feedback and extremely high gain. It's also an approximation only and is invalid if the op-...
• 407k

### Issues with Audio Amplifier Circuit - No Output Signal with Capacitor, noise

I'm not sure how you expect Q2/Q3 to work, but with just a pullup resistor to the base they're going to be turned on all the time. Only the largest of negative signal peaks are going to produce a ...
• 5,836
Accepted

### How to solder the central pin of the TGA 2214-CP microwave amplifier

Page 11 tells you to solder the module manually. Do not use a reflow oven or hot air. The drawing of the evaluation board shows that the solder pads are a bit longer than the pins. That makes it ...
• 72.5k

### Why should the Vce be half the value of the supply source?

This statement (Vce = Vc = Vcc/2) is valid for a CE stage with grounded emitter. If there is an emitter resistor inserted, then Vc = (Vcc - Ve)/2 + Ve = (Vcc + Ve)/2.
• 17.5k
Accepted

### Why does the voltage increase when I connect this amplifier to a gate driver?

You're going to need to drive both the high and low harder. With your circuit a current of 100 uA, which is within the gate driver's specced input high range, will drop 3.9 V across the collector ...
• 25.1k
Accepted

### What happens when you insert an inductor between Vcc and a MOSFET's drain?

I think there are a couple of big reasons why you are not able to predict the voltages present in your simulation: Maximum current through the inductor and MOSFET is ambiguous, since $R_{DS}$ is ...
• 39k

### What happens when you insert an inductor between Vcc and a MOSFET's drain?

Assuming an ideal switch, we can analyze this with a two-phase solution. Assume initial conditions from the previous cycle (periodic steady state). While the switch is on, ...
• 39.6k
Accepted

### LTSpice simulation produced different results of phase margin when using step-signal % overshoot technique vs loop analysis technique

The phase-shift at ~0 dB is ~ 99 degrees. This equals to phase margin of 99 degrees (right?) You may be interpreting the results of the AC simulation incorrectly. It seems you have followed the ...
• 5,327
Accepted

### What is the purpose of the diode in this complementary class B amplifier?

The purpose of the diode to reduce the crossover distortion. The diodes make sure that both of the transistors base-emitter voltages to be set for linear operation. This reduces corssover distortion ...
• 2,593
Accepted

### Are there safety concerns with hooking an inductor to a MOSFET and generating 85V spikes from a 9V source?

The breadboard will probably be fine, but anything above ~30VDC cannot be considered touch safe. In addition, the circuit you have does not regulate its output so the 85V figure could be low or high ...
• 20.3k

### How a car inverter can diffuse 16 A 230 V if the input is a 12 V car battery?

That's the maximum current rating for the connector. It does not represent the maximum current the inverter can supply. If the datasheet states the inverter is capable of providing 500W, then the ...
• 67.8k

### Why should the Vce be half the value of the supply source?

It depends essentially on a few considerations: What's the available power supply voltage difference across the circuit? What's the input signal voltage range? What's the gain required? (Or, what's ...
• 11.2k

### How can a Class E Power Amplifier be built and experimented with safely?

basically be very carefull Follow the same advice given to those working with vacuum tubes. rubber shoes and one hand behind your back.
• 34.6k

### Why does a MOSFET fail on fast signals, even if they're much longer than the turn on + turn off times?

While you may not have drawn a resistor in series with V2, the mosfet model most certainly contains one. See LTSPICE wiki: https://ltwiki.org/LTspiceHelp/LTspiceHelp/M_MOSFET.htm which in the table ...
• 153

### How would one calculate the transconductance of the FETs in this circuit?

The two formulas you show are correct. But you can't compute $g_m$ without knowing $V_{\text{GS}}$. And you need the DC operating point to tell you that value. That means you must work out the DC ...
• 11.2k
Accepted

### Why do direct conversion receivers amplify only after mixing?

I understand that we want to defer some of the amplification until after the final filtering, so that we amplify only the signal, and do not have nonlinearities and intermodulation to deal with, and ...
• 26.7k
Accepted

### Determining the zeros and poles of a common emitter amplifier

I have gone through the derivation of the transfer function of this transistor-based amplifier, including the dc-block capacitors and the two parasitic contributors. Needless to say that without the ...
• 22.7k

### Is it correct to apply KVL through the 2 inputs of an op amp?

Short answer The circuit presented by OP is a constant current source that supplies a "floating" load and a current-setting resistor R in series. The voltage across the resistor is formed as ...
• 17.5k
1 vote

### Is it correct to apply KVL through the 2 inputs of an op amp?

are we allowed to apply KVL by jumping between wires? Yes of course. At every element along the KVL path, we jump from the wire connected to one terminal to the wire connected the other terminal. The ...
• 17k
1 vote
Accepted

### Filter for supply voltage of amplifiers

Yes, use some R-C (or L-C) filtering on power supplies. You should use a circuit like this one. Be sure that the ground should be as nearest the supplies pins (possibly "between"). Sometimes,...
• 14.5k
1 vote
Accepted

### How can a Class E Power Amplifier be built and experimented with safely?

OP's circuit does generate voltage spikes at MOSfet drain that can considerably exceed the DC supply voltage. Switching current off quickly to an inductor is the cause. The circuit fragment of the few-...
• 26.7k
1 vote