Tagged Questions

2
votes
1answer
84 views

Analysis of Shunt Circuit

I am having trouble computing the closed loop gain of the circuit below: It seems clear that this configuration is a Shunt Voltage but I just can't figure a way of computing the feedback factor and ...
0
votes
1answer
75 views

Planning an amplifier using a transistor

I want to plan design an amplifier of tension voltage using a transistor: but I don't know how I can choose the values of \$R_1\$, \$R_2\$, \$R_3\$, \$R_4\$, \$C_1\$ and \$C_2\$.. I want to obtain ...
3
votes
1answer
152 views

BJT Differential Amplifier-Long Tailed Pair

I am trying to solve this assignment Consider this schematic (the BJT's are in the effective area, with \$\beta=200\$ so as to \$i_e\approx i_c\$). Also \$R_1>>R_E+r_e\$. Define ...
-6
votes
2answers
126 views

Simple amplifier Cuircuit [closed]

I am new in electrical transistors. My project is to make a 1 watt audio amplifier. Can anyone provide a best amplifier circuit using darlington pair and 2N3904 transistor. i searched google. So ...
0
votes
0answers
45 views

Amplifier circuit - NMOS mode of operation? Gain?

Ok I have the following circuit, with values of variables: \$\displaystyle R_{1} = 1 M\Omega, R_{2}=10k\Omega,~~ k_{n}C_{ox}\frac{W}{L}=1mA/V^2\$ , and \$V_{T}=1V\$. 1) When \$v_{IN}=0\$, calculate ...
0
votes
3answers
176 views

Input impedance is higher in Common-Emitter than Common-Base?

Why is input impedance is higher in Common-Emitter configuration as compared to Common-Base configuration as signal is applied on Base-Emitter junction in both Amplifiers. Not in both configurations ...
8
votes
4answers
174 views

Flow of holes in transistor?

Bipolar transistor are said to have both electron and holes flow. Movement of electrons can be understood but holes are fixed part of the atomic/crystal structure.How can we characterize their ...
7
votes
1answer
1k views

Can the Common Emmiter Amplifier use a PNP Transistor instead?

This is a simple Class A amplifier using an NPN transistor: Is there a way this can use a PNP transistor, instead (with only 0V and +Vcc, not 0V and -Vcc)? Why or why not?
4
votes
3answers
149 views

Whats the role of these transistors

I'm asked to explain what the function of transistors Q1-Q2 and Q3-Q13 are. So far i've been unable to figure it out. If you know what the functions are, please also tell my how you derived it.
-1
votes
1answer
212 views

Design rules for power AB amplifier stage [closed]

could you please point me to a good guide for a simple class AB power amplifier design based on BJTs (referring to the "classic" schema with complementary push pull, diodes to remove cross over, ...
3
votes
3answers
213 views

Polarized capacitors in common emitter amplifier

This is the basic common emitter amplifier.I have read that polarized capacitors should have proper polarity connected to terminals of DC voltage source and they may blow off if they are connected ...
2
votes
2answers
188 views

technology to search small objects like pendrive, key-chains etc

I am a web developer by profession. few days back I lost 8gb pen-drive :( I don't it is in home or somewhere else.... So now I am thinking of a device which can be attached with small objects so that ...
2
votes
3answers
545 views

common collector amplifier

In common collector amplifier, we know that the collector is commons since it is connected to AC ground. Now, the characteristics of a common collector amplifier is that it has unity voltage gain, to ...
0
votes
4answers
182 views

put more juice in the speaker

Above is a push pull Amplifier. As we all know the 8 ohm speaker is not receiving enough juice from the supply rails, in fact its only getting around 16 watts of power, how can we double that amount ...
0
votes
1answer
89 views

output signal now became smaller

Why is that without the power amplifier block connected to the output of preamplifier, the output signal is ok around 17 volts peak to peak, but if i now connect the power amplifier, the signal ...
0
votes
1answer
150 views

q point keeps shifting when there is input signal

Why is that, even at transistor idle conditions, where my q point is exactly midway in the transistor loadline, when i start to inject ac signal at the input, the q point starts to shift somewhere ...
1
vote
4answers
3k views

How to increase current of a DC circuit

Well.I am new to electronics. I have just started creating small circuits. Coming to the point,I have a circuit with 5v input and current in the circuit is 2ma but I have a requirement to increase ...
6
votes
1answer
213 views

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 ...
20
votes
2answers
475 views

What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?

For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the ...
4
votes
2answers
560 views

What transistor should I use to power a motor from an xbee

I have a small motor what operates at 3.3V at 50mA (sorry no documentation) and a Xbee radio which outputs 1mW. I would like to allow the Digital I/O pins output on the Xbee to drive the motor ...
6
votes
4answers
574 views

Alternatives to transistors

I'm trying to think of alternatives to transistors, simply because I'm curious. I don't care so much about the amplifying characteristics of transistors as their ability to make logic gates. Here's ...
6
votes
3answers
425 views

Controlling a current with another - home-made alternatives to the transistor?

I have a very basic understanding of how a BJT or a FET works, but I think I got the idea. They are awesome in all regards, except one: you can't make one at home without hot ovens and scary ...
0
votes
2answers
297 views

Power Calculation of an Amplifier

Here is a simple audio amp. Is there an easy way to calculate the power it gives? edit Resistor value, input level and speaker impedance changed.
2
votes
4answers
768 views

Common Emitter Audio Amplifier

I'm tring to build an audio amplifier. I decided to use a basic common emitter amplifier circuit as a starting point. Here it is: I have some questions about the circuit. 1-) What transistor can I ...
-1
votes
3answers
313 views

Calculating the power of a simple amplifier

I found this circuit on internet. It says it's a 1w amplifier. There is no explanation about how that is calculated. How could the power of this circuit calcuted? (input is a radio) And is there any ...
1
vote
2answers
106 views

Amplifier theoretical analysis problem

I have this problem in a book and I've did good through the entire problem until I had to calculate current gain. I've been stuck for the past 30 minutes. The formula I get is different from the one ...
0
votes
1answer
231 views

Voltage source for single transistor audio amplifier

Here is a simple audio amplifier with an npn transistor. What should be the value of voltage source V2? How can I calculte it?
-2
votes
0answers
68 views

Basic audio amplifer circuit with transistors [duplicate]

Possible Duplicate: Simple Audio amplifier Using Transistors I'm looking for a basic audio amplifier(1w - 0.5w) circuit which is designed with transistors. Could you help about that?
-1
votes
1answer
1k views

How to amplify an electret microphone

I need to amplify an electret microphone for use with an Arduino Uno. I have a few capacitors and resistors and several transistors one of which is an N-channel. Any ideas? Can you please also provide ...
5
votes
1answer
1k views

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?
1
vote
2answers
309 views

detecting low signal levels with a transistor

This question made me wonder. Say I want to drive a LED when a small level audio signal is present. I understand how to do this with an opamp, but how about a transistor. You'd have to bias it so that ...
-2
votes
1answer
924 views

How does transistor amplify current? [duplicate]

Possible Duplicate: I don't care how a transistor works, how do I get one to work? Basic questions about transistor amplification I have heard transistors are used in many electronic ...
7
votes
5answers
5k views

Simple Audio amplifier Using Transistors

I would like to build a simple audio amplifier using transistors. I know there are IC designs specifically for the task. But i want to use transistors so i can learn how to use them for amplification. ...
1
vote
2answers
524 views

1.8v GPIO controlling 5v 10mA solid state relay

I have a Crouzet 84 134 900 solid state relay that I need to control with a 1,8V GPIO output from a Gumstix Overo Summit expansion board. I've tried the circuit drawn up for me in this answer, however ...
2
votes
2answers
297 views

npn transistor base current question

Hi i am new to using transistors for signal amplification. Can someone explain to me how to figure out the amount of current being drawn into the base of the transistor when it is in the common ...
2
votes
1answer
976 views

Intrinsic Gain vs. Voltage Gain

I was wondering what the difference is between intrinsic gain and just "normal" voltage gain of a circuit i.e Vout/Vin? thanks
1
vote
2answers
660 views

Operation Amplifier with Transistor output

Is there a name for feedback amplifier topologies which include an opamp and transistor in the feed-forward path?. I need to design an amplifier with high bandwidth (almost 100 MHz) and high gain (50) ...
2
votes
3answers
435 views

Solving DC Operating Point of Common Source Amp

My lab partner and I are really stumped. We are given a circuit that has a FET with a \$V_{DD} = -V_{SS} = 15\mbox{ }V\$. We are told \$A_V = 20\$ and \$I_{DS} = 1\mbox{ }mA\$. The DC circuit is ...
3
votes
1answer
579 views

Testing an Audio Power Amp with Paralleled Transistors

A question concerning my current repair project of an audio amp that uses big (600 W) but otherwise rather classic complementary output stages: I assume when testing an audio power amp with 6 pairs ...