# Tagged Questions

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### How to design a schematic diagram of amplifier that can drive 8 ohms 0.25 Watts speaker? [on hold]

I have here a schematic diagram for amplifier that drives a 0.025watts 8ohms speaker. But what I need is an amplifier that drives a 0.25 watts 8 ohms speaker. So, here are my concerns: How can I ...
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### BJT audio amplifier for 8 ohms 0.025 watts speaker

I have to analyze an amplifier circuit for 8 ohms, 0.025 watts speaker and don't understand how it works. What is the working principle of the components? What configurations are used? In which stage ...
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### Intrinsic resistances of a BJT amplifier: how find them?

I'm studying the low-frequency response of a BJT amplifier. I can't understand how I can find, for example, corner frequency $\omega_{P1}=\frac{1}{C_{C1}[R_B || r_{\pi}+R_{sig}]}$ where ...
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### Designing yet another BJT amplifier given some constraints

Sorry for asking a question about the same subject as my last question, but I am once again stuck on a BJT Amplifier design problem. Where the beta parameter may vary from 100 to 800, the voltage ...
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### Designing a BJT Amplifier given some constraints

I am trying to design a BJT amplifier following this model: Where the beta parameter may vary from 100 to 800, the voltage between the base and the emitter equals 0.6V (active mode), $V_t = 25 mV$ ...
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### How to control the gain of FET/BJT/Op-Amp amplifier by input voltage range?

Assume I have an input voltage ranging from 5-10 MHz and want to amplify it. The case is pretty simple as any device as FET,BJT or high frequency op-amp can do the amplification well but I have a ...
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### Zener Noise Generator - NPN BJT Amplifier Analysis

I'm interested in creating a low voltage white noise generator by means of a zener diode, as detailed here: Zener & BJT Noise Generator. Specifically, I want to use the circuit here, in order to ...
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### What's the difference between small signal bipolar junction transistors (BJTs) marketed as switches vs. amplifiers?

For instance, the MMBT3904 and MMBT3906 BJTs are listed as NPN/PNP Switching Transistors, and the datasheets mention the switching times, while the BC846 and BC856 BJTs are listed as NPN/PNP general ...
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### Do two stage common emitter current amplifiers add or multiply?

So I've seen alot of explanations on two stage voltage amplifiers and how how their gains can be multiplied together. My question is when you are using a two stage common emitter amplifier for current ...
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### BJT in Reverse Active Mode of Operation

What will happen if for a BJT transistor it's Emitter terminal is treated as collector and collector as Emitter in a common Emitter amplifier circuit?
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### Short circuit protection in simple audio current amplifier

In my class, we are to design a current amplifier with short circuit protection. In our design, we utilized 2 emitter follower amplifiers (Q3, and Q1). We then added Q4 and Q7 to lighten the current ...
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### I don't quite understand this FET-BJT preamp circuit

I see this circuit a lot on electret microphone preamps, but I don't quite understand it. The FET is operated as a common source amplifier, so it has gain, inverts, and has relatively high output ...