# Info about working with RF tuning amplifier

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#### Charlie_Brown

##### Newbie level 6
Heloo I am doing a proyect and I d´ont know how to work with RF tuning amplifier. I woould be pleased ijf anyone help me.(give me some information or a web)

### Charlie_Brown

Points: 2

#### Borber

rf+amplifier+collector+inductor+value

What is RF tunning amplifier? Do you mean tunned amplifier? Post schematics.

#### Charlie_Brown

##### Newbie level 6
tuning tank circuit

This is the fist step in a reception of ultrasound. I do not know how analize this circuit. I need something similar to my proyect, I want to demodulate sounds for a ultrasound wave.

this is the circuit ,sorry

#### Borber

rf tunned amlifier

This is a tunned amplifier. LC tank in collector is a resonator and determines frequency characteristic of amplifier. It amplifies a narrow band frequencies arround tank resonance. Amplifier is selective with center frequency 5MHz. If you want to amplify ultrasound you must know the frequency of signal. It can be 40kHz for example and the resonance frequency of tank circuit must be the same.
Resonance frequency of tank circuit is:

f=1/(2*pi*sqrt(L*C)) sqrt stays for square roote

I would use 10mH inductor and 1.5nF capacitor. Inductor must be variable.

Tunning is simple. Connect a ultrasound signal to the input and connect an oscilloscope to collector of the amplifier and vary inductance to get maximal output signal amplitude.

### Charlie_Brown

Points: 2

#### Charlie_Brown

##### Newbie level 6
tunned amplifiers

You explained very goog.Thanks you.I suppose that with a similar circuit you can make a small radio,d´ont you?Well, and I have another little dougbt, you explainde the capacitor and the inductor that are in the collector. why is used the capacitor of 1nF and why the values of the emitter are those?It´s the configuration of the amplifier?thank you very much

#### Borber

tuned rf ampl

Values of L and C in tank circuit are linked by formula for resonance frequency. But here exist another term that describes tank properties. It is Q factor or quality factor. Q depends on values of L, C and tank losses. Greater the Q narrover is the passband of the amlifier. For above example I choosed usual amplifier bandwidth.
Detailed theory of LC resonators you should learn from books.

Emitter resistor so as other resistors arround the transistor in circuit are calculated for temperature stability of transistor operating point.

### Charlie_Brown

Points: 2

#### Charlie_Brown

##### Newbie level 6
rf tank circuit amplifier

ok;I will try to learn something more about LC,it seems very interesting!!. With my proyect I am using ultrasounds of 40Khz, in datasheets put that my recepctor has a narrow band(around 40Khz) I dónt think that woll be a lot of problems. I am trying to get sounds of the inside of an egg with a chick. I am thinking in get with this circuit the wave of ultrasounds modified with that little information(the movement of the heart of my chick), and eliminate noise , it seems a difficult job,what do you think?do you think will be possible?THanks

#### Borber

pi-tank tuning

I didn't get a picture of what you are intend to do. Are you trying to make ultrasound radar or scanner? Chicken heart is not producing ultrasound I think.

#### Charlie_Brown

##### Newbie level 6
ultrasonic capacitor inductance

Now i Can not send any circuit but I´ll do it. I am going to base my proyect in Doppler echos. I am looking another proyect, and I can do it like they do with humans.

#### Borber

rf tank circuit

I see. Good luck.

#### Mike zhang

##### Junior Member level 1

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