Questions tagged [common-emitter]
A common emitter is one of three basic bipolar junction transistor (BJT) amplifier topologies. It is notorious for a high power gain. It is the only one-stage BJT amplifier topology that permits gain both in voltage and current.
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NPN Transistor Base Current Calculation from Beta, Vth, and Rth
In this answered question regarding a common emitter NPN Transistor....
NPN Transistor common emitter calculation
I am struggling to understand the section "Assuming Active Mode"
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Problems with choosing resistors for a common emitter - voltage divider bias amplifier circuit
I'm designing a common emitter - voltage divider bias amplifier circuit like below:
Requirements:
\$|A_v| = 5\$
\$Z_{in} \geqslant 10k\Omega\$
\$P_{consumption} \leqslant 0.2W\$
\$V_{CC} = 15V\$
...
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Audio switch using NMOS (low level signal)
A common-emitter amplifier can include a bypass capacitor from the emitter to ground, resulting in considerable extra gain (1000uF in the picture). What happens if the bypass capacitor is switched &...
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Transistor Driver - what is the purpose of Q2 on the included schematic?
I saw this schematic at the link below and I would like to know if there is any use in particular for Q2. Since the transistor Q2 is just, somehow, operating as a simple diode that is following the ...
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How does resistance limit the gain in a common emitter amplifier? [closed]
I am having trouble understanding common emitter amplifiers.
Can someone please explain how RE1 is limiting the gain of the amplifier in this circuit?
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How to design BJT common collector amplifier?
I am working on a school project and I am struggling to design what is supposed to be an easy CC-amplifier. All other parts of the circuit are calculated and should work. The power amplifier is what's ...
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How can I eliminate cut-off [closed]
I have built a multistage bjt circuit. I got my gain to be around 40, but I cannot figure out how to eliminate the cut-off. The only values I can change are the resistor values (except the 50kOhm ...
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What causes a negative voltage dip on the collector of common emitter NPN circuit at turn-off?
Circuit diagram:
simulate this circuit – Schematic created using CircuitLab
Observed waveforms:
(Yellow: 3.3V square wave in, Magenta: Collector output)
When the input square wave goes low and ...
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Output characteristics of a BJT
While plotting the output characteristics of a CE configuration, the graph between VCE and IC, it shows that when VCE=0,IC=0 My doubt is whether VCE=0 means we are shorting collector and emitter or ...
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Current mirrors with the voltage amplifiers
I am having a slight confusion with the current mirrors and their use with the common emitter amplifier. I have seen that the current mirrors can be used to bias the circuits and replace the need for ...
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Why do we need a resistor across the transistor base-emitter junction?
I am still not very good at some of the basics. Why do we need the bottom resistor across VBE when the voltage drop is always 0.6 V (as VBE is acting as a forward bias in parallel to the resistor)?
If ...
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Single stage common emitter amplifier output voltage
I am having trouble getting the voltage Vout=1.25v and the gain should be Av=5 and I have the input voltage Vin = 0.25v. This is my schematic, what did I go wrong?
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Stability factor and stiffness of voltage divider on a transitor
Does stability factor and stiffness of the bias network have a connection? this site mentioned something about stability factor so i was wondering if its thesame thumb rule about the current in ...
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Highest DC current gain
I drew a circuit with a transistor (ktc3198) at heart for getting the highest DC gain the transistor can offer. I used its input and output characteristics.
And based on that I made a little circuit. ...
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Multistage common-emitter 2N4401 amplifier
I am trying to design a common-emitter multistage amplifier with gain 40 given \$V_s(t)=0.25\sin(2\pi 1000t)\$ and \$V_o(t)=-10\sin(2\pi 1000t)\$. Vcc is 24v and I want my q-point to be Vce=12v. I ...
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Stage of Amplification In BJT [closed]
For a common emitter current amplifier, at what point, stage, or junction does is applied current amplified?
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How can I bias the two transistors (Q59, Q58) two main transistors in my common emitter pnp amplifier? [duplicate]
[
I tried in my design to make a common emitter stage amplifier using a pnp transistor and a npn transistor as a current source but I didn't know to bias either of them (well as for Q54 I think I've ...
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Common Emitter Amplifier DC analysis
I have a standard common emitter amplifier biased using a voltage divider. I'm given that RE = 500 Ω, IC = 2.5mA, β=100, Vcc=15V and the coefficient of thermal stability K=10 (RE = K * Rth / (b+1) ...
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Troubleshooting class AB amp with only multimeter
I made a stereo amplifier on a PCB which is two of the following circuit.
One channel amplifies the audio decently, but the other channel has NO sound regardless of how loud I make the input.
My sound ...
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Is it misleading to say a common emitter amplifier is “out-of-phase”?
I now understand that a common emitter amplifier produces an inverted amplification. I am asking this question because for a bit, I was hung up around the frequency with which I heard it explained as ...
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My RF amplifier circuit works in LTSpice. Will it work in reality, too?
I am working now for a while with bias calculations. I have found a good turorial to calculate it by my own and I have seen that there are already calculators on internet, which made my life much ...
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Biasing a BJT in a common emitter amplifier
I'm trying to design this common emitter amplifier to have a Q-point of \$(V_C=2.5 V, I_C = 2.5 mA)\$. According to my calculations (see below), if I were to use \$R_2 = 100 k\Omega\$, I should also ...
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Common Emitter small signal model for high frequencies simplification
While trying to calculate the high frequency pole frequency corner of the common emitter amplifier I came across the following small signal model (found here in page 332)
The small signal equivalent ...
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High gain low current amp
I'm trying to design high gain, low collector current Common Emitter amplifier.
As far as I know, this is well known CE amp for high gain.
Is there anything I can do for low-current consumption? And ...
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Signal saturating after transistor amplifier
I'm trying to amplify this noise coming from Q1 but it looks like it's saturating at the collector of Q2 (as you can see in the image). How can I resize the resistor values such that the signal does ...
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What goes on inside the transistor that amplifies the signal?
I understand that, for example, in BJT NPN transistor in common emitter configuration used as amplifier, feeding the small signal at the base will produce the larger signal at the collector.
But what ...
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How to correctly bias an NPN transistor without allowing base voltage to be too high
simulate this circuit – Schematic created using CircuitLab
I am trying to correctly bias a BC337 NPN whose collector is connected to a 9V source. I wish to use it as a switch in response to a ...
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BJT amplifier design
I am trying to design a BJT amplifier with the given parameters and limitations. The circuit is shown below.
Parameters:
Vcc = 15 V
RL = 20 kΩ
beta = 180
Vbe(on)= 0.6 V
Cµ = Cπ = 0
Limitations are:
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Common emitter configuration opposite
What is the simplest circuit of common emitter configuration inverse that is switching to open on high base current and to close/shorted on no/low base current?
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Active load role on this circuit and possible uses
simulate this circuit – Schematic created using CircuitLab
I came with this circuit to know how an active load can improve it, I still can't finish to understand the role of active loads. The ...
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Output voltage for operational amplifier goes to supply rails
I've been trying to understand the innards of an op amp and I'm having a hard time understanding why the output looked clipped.
Below is the schematic I got from Hackaday. I've simulated this in ...
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How does a transistor inverter work?
When the base of the transistor is LOW, no current can pass through the collector to the emitter and therefore if the current is 0 the voltage is 0 and all current will pass through the resistor that ...
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LTspice expression, need voltage value at a different time
Using algebraic expressions (right clicking in trace window header to enter arbitrary formulas), I am trying to plot the gain over time of a simple BJT-based common-emitter amplifier.
As is well known,...
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How to determine \$\tau\$ for such a case?
In the above circuit when I want to calculate the impedance seen by each of the capacitors, should I short or open the other one? Or which ever one is more convenient?
In order to find \$\small f_{C_E}...
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MOSFET with resistor degeneration (Rs)
This is the two-port equivalent circuit of a CE amplifier with resistor degeneration (circuit 1).
Will this just be the same in a MOSFET? What if the ro is approaching infinity in the MOSFET, is the ...
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How to drive a small 8 Ω load given a CE-CE amplifier?
I want to amplify a 25 mVpp input signal with a source resistance of 1 kΩ to anywhere from 2.5 Vpp to 3 Vpp to drive an 8 Ω load (though at this point I am willing to sacrifice gain to just drive my ...
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Operating point for high current transistors
I'm a neophyte self-thaught learning electronics. I'm trying to amplify a DC current from a little less than 1 to 8 A using an NPN transistor. Currently I'm trying to figure out how even could I ...
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DM and CM EMI emissions measurement in LTspice
according to a youtube video V(SMA1,SMA2) is equal to 2DM_noise and V(SMA1)+v(SMA2) is equal to 2CM_noise. it is said that they must be divided by 2 and also multiplied by 1,000,000 to result in dBuV ...
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How to calculate the quiescent current of a common emitter amplifier
Given the supplied circuit - I'm trying to work how to calculate the quiescent current.
All values are known. I've already done it in SPICE but really would like to know what the formula looks like!
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Common emitter transistor amplifier working in simulation but not in reality
I'm currently learning about transistor amplifiers. I've designed this CE amplifier circuit that should yield an ac voltage gain close to 100.
I assume my calculations where right, as it seems to ...
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How does this voltage divider work?
I'm trying to understand how this voltage divider works with an NPN transistor in it.
If there were no transistor, V_OUT = 10.2 * 5.1k / (5.1k + 1.8k) = 7.54V
Reference to ground 7.54 - 5.1 = 2.44 V
...
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Why is this a common collector transistor circuit?
This is a common collector transistor circuit:
This is a common-emitter transistor circuit:
Consider the following transistor circuit:
This transistor circuit looks an awful lot like a common-...
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trouble understanding thevenin equivalent
I really don't understand how the middle ciruit is the thevenin equivalent of the left-most circuit, any help?
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How does the common emitter configuration offer higher output impedance?
I know that the base-collector region is reverse biased and because of that it offers high resistance but it is the resistance due to biasing.
In a video, the person was explaining the hybrid-pi model ...
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How to calculate the output resistance of the CE amplifier, which has only a coil in its collector?
In order to be able to match the impedance, it is necessary to know the output resistance of the amplifier.
In radio frequency amplifier circuits, there is usually a coil in the collector instead of a ...
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Wrong calculation of collector current
There is a transistor circuit which I am DC analysing.
I did KVL to find base current.
-5 + Ib.10k + Vbe(0.7V) = 0
Ib = 0.43mA
Hfe of NPN transistor is 100.
Ic = hfe.IB, Ic = 0.43mA*100
Ic = 43mA
But ...
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Common-Emitter Analysis
I am making an error in the analysis of the above circuit.
$$i_i=i_b \implies v_1=i_b\cdot r_{\pi}$$
So the value of $$g_m v_1 = g_m\cdot r_{\pi}i _b= \beta i_b$$
But, this is the same current (\$i_c =...
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Why does my transistor explode in a simulator?
I'm new to electronics and I can't identify the reason why my transistor explodes when I simulate it.
I am simulating a simple common emitter amplifier with a power supply of 12 volts.
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Designing the first stage (common emitter) of an amplifier that will drive an 8 ohm speaker
I have to design an amplifier (can be one stage or multiple thought I am thinking multiple) that will drive an 8-ohm speaker and have a gain of at least 10 V/V (about 20 dB) given Vcc = 9 V. It also ...
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Why is the cut off voltage on the AC load line lower?
I know the AC loadline is steeper because the load resistance \$r_c = R_C||R_L\$ is low, but a low resistance DOESN'T shift the cutoff voltage. That is because when the BJT is OFF, all the supply ...
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