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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.
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
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.
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