Author Topic: What is minimal amount of connections inside a 4-pole to have gain > 1?  (Read 735 times)

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Online dusanTopic starter

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I have a theoretical question. Consider this 4-pole black box, what connections inside it are required for it to have gain more than 1?



I am only certain about 2 connections:

1. there must be connection between input and output (otherwise signal would not be able to pass.

2. there must be connection between vcc and out (otherwise there would be no gain > 1, it needs power)

But I'm not sure about other connections. It is possible to have gain > 1 without:

3. gnd to out
4. vcc to gnd
5. in to gnd
6. in to vcc

« Last Edit: December 04, 2023, 11:36:11 am by dusan »
 

Offline NiHaoMike

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Re: What is minimal amount of connections inside a 4-pole to have gain > 1?
« Reply #1 on: December 04, 2023, 12:15:15 pm »
Voltage gain, current gain, or power gain? A transformer can be used to increase voltage or current with no power supply other than the signal itself.
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Offline wraper

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Re: What is minimal amount of connections inside a 4-pole to have gain > 1?
« Reply #2 on: December 04, 2023, 12:29:46 pm »
It is possible to have voltage or current gain with just 3 terminals. In, out and either GND or VCC. To amplify power, you will need all 4.

 

Offline NiHaoMike

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Re: What is minimal amount of connections inside a 4-pole to have gain > 1?
« Reply #3 on: December 04, 2023, 12:44:08 pm »
Thinking about it some more, if the input has multiple frequencies and you're only interested in a subset of them, you can use the power in the other signals to boost the signals you're interested in. I recall someone successfully used one crystal radio tuned to a strong station to power a single transistor amplifier for another crystal radio tuned to a weaker station.
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Offline wraper

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Re: What is minimal amount of connections inside a 4-pole to have gain > 1?
« Reply #4 on: December 04, 2023, 01:27:16 pm »
Thinking about it some more, if the input has multiple frequencies and you're only interested in a subset of them, you can use the power in the other signals to boost the signals you're interested in. I recall someone successfully used one crystal radio tuned to a strong station to power a single transistor amplifier for another crystal radio tuned to a weaker station.
Well, if you start applying certain conditions, by adding a resistor in series with VCC (or GND) you can combine power supply with signal output. But it's not what is shown in question.
« Last Edit: December 04, 2023, 01:31:23 pm by wraper »
 

Online ebastler

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Re: What is minimal amount of connections inside a 4-pole to have gain > 1?
« Reply #5 on: December 07, 2023, 10:10:03 pm »
Voltage gain, current gain, or power gain?

Good question. I have heard that they sell backbox devices, e.g. for improving your mains outlet's power efficiency/cleanliness/whatever -- with zero connections inside, and with high fincancial gain.  8)
 


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