Transistorized DC amplifier

[mercurial]

I will recalculate it better, with formulas and adding polarization.

Hi
You use the term polarization, is it same as biasing a transistor?

[Picuino]

Yes.

[Picuino]

Some theory about feedback amplifiers:
 * https://testbook.com/physics/feedback-amplifier
 * https://www.jntua.ac.in/gate-online-classes/registration/downloads/material/a159298350984.pdf
 * https://www.geeksforgeeks.org/feedback-amplifiers/

Although the best way to study these concepts is a good book like the one I attached above (Gray - Meyer).

[Zero999]

Another feedback topology more linear.

https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgpABZsKBTAWjDACgAXcDQ8MFEChQ0+AqhBbZo2MDRpgElYQkL4RMBNmIo8kBBkgk8NfEhSUQAEwYAzAIYBXADYc2ANyiCTnsLypVvBU9-aAQ2AHdPYSpCEWioCJ9eMB5wP0TYtPFU3393EEz4zNyfWnFQ8AqQsMjC7yE470hEzAFWAWw0UQSTemxsXl1aYrlPDAB9fjxxyHGADzwwSH5xhBnYeDJCFXNxlnGUA73iaYnsdfhIGlIb27viQhmMkRLinR7IPoFi1XB3qmIkx0M3mi2WhzWMEuWx2a32h0OTBw40B5yh8Gu9yxDyeXAaIAeggwAkJVBYfGgeEIKGwGBUeB4hEIAzwICYMGZBgwxGwNCEVJU5CWVGs9mcrgAToJhNxePj4uI4C0ZSk5Sr-i1ibLpS9Us1Iq0QENDb4Egatab8abmlKrWqRKTkPA2JZte03b8BKLHC42FLVWk3fwfM7IgHLSr0raLcGTXqys0gA

https://tinyurl.com/2xjqa4uf

Current feedback is a good idea. It's also possible to design such a circuit with a high bandwidth.

The gain is a little off. Remember A_V = 1+R_f/R_g

I would replace the diode with an emitter follower to increase the input impedance.



 3V to 12V discrete.asc (1.43 kB - downloaded 16 times.)

Hi

I understand that there are topologies like Common Emitter, Common Base and Common Collector for AC amplifiers. I'm sure that can also be used for DC input.

I was looking at converting a 0 to 3V DC input to 0 to 12V output using transistor amplifier stages.
Are there any alternative topologies and guidelines for dc amplification?
Any general rules to approach the design of operating point and calculation the output?

Or are the same trio of topologies as given above suited for dc amplification.

Just one question: why?

Use a single supply op-amp, such as the LM358.


A_V = 1+R_f/R_g

For a gain of 4:
R_f = 30k
R_g = 10k

[Picuino]

https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcDoBYDsAmdA2dBOdMMADhzEnxAUmpFQGZqBTAWmICgAXcXcMTCEyZU-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

[Picuino]

https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWEBmAHAJmgdgGzoRmACzICcpkORICkNIJNApgLRhgBQAblCOlul5FUvOkTpgkdadAQcA7r36CqfAVAVCR6dNWEbFqsDgnoRx6dxCrl16hd7IGE2eFcy5h6rZ3f1kTVtiamR0CSJqAPEnUIkwQQjzXF4cAH141FTIVIAPVHZ41IQs2HhSXAQ8YrZU9FrUlixkVLTmmHhIInJunt7SNICvcBM7cDMNaJQVexGM3kyMrNz89jri9rKKqoawerrG5sy20rguvvP+rI5xUnBk4LVBB6cYHFFYdGQwDp+OwXRNHMHEDxoMxuZxmB7qDAro7m9fI8DHw4asUXoRAEAE5Ih4+SCYlDwDg4-HadS2CTExSInwU-yBCkE+F8ZlgqFvYHJMKYjhAA

[Picuino]

The operational scheme is better at reaching the limiting voltages and is more linear, but its response is much slower for high frequencies.
The scheme with two transistors can amplify without problems frequencies of 1MHz or more, which would be very difficult to achieve with the operational.

[Zero999]

The operational scheme is better at reaching the limiting voltages and is more linear, but its response is much slower for high frequencies.
The scheme with two transistors can amplify without problems frequencies of 1MHz or more, which would be very difficult to achieve with the operational.

It depends on the op-amp and the slew rate.

What we have here is a type of current feedback amplifier, as I hinted in my previous post. The speed is limited by the turn-off time of Q3, so one can expect it to have a fast rise time and slow fall time. It has a wide bandwidth for low amplitude signals, but will suffer from slew rate distortion, with large amplitude, high frequency signals.

Pulling Q3's base up via a current source and reducing the resistor values will speed the circuit up, at the cost of more parts, higher power consumption and a lower input impedance.

A real current feedback operational amplifier has a push-pull output and the transistors are pulled up by current sources, giving a fast slew rate for negative, as well as positive output swing.

I've done an AC analysis. There's a peak around 10MHz, which indicates some resonance/oscillation.

 3V to 12V discrete AC.asc (1.59 kB - downloaded 4 times.)

The transient analysis shows a bit of over/undershoot. Note the fast rise time and sluggish fall time.

 3V to 12V discrete tran.asc (1.51 kB - downloaded 2 times.)