1st Lesson: Single-tuner resonant amplifier circuit
A. Experiment aim
1．Get familiar with the composing of Single-tuner resonant amplifier circuit and usage. 2．Test its performance parameters that take place the resonance.
3．Mastering the principle of high-frequency low signal tuner amplifier and the methods on designing high-frequency signal amplifiers.
B. Apparatus
1、 2、 3、
Oscillograph one Digital multimeter one
High-frequency experimentation case one
C. Experimental circuit principle
This experiment consult circuit diagram 1-1, using emitter to a total of Law. Load of collector of transistor is parallel resonance LC which can do the work of amplifying and frequency choosing at the same time. In the circuit, the standard point of the transistor depends on resistance of RB1, RB2 & RE.
The characteristics of tuner amplifier is the load of amplifier being not pure resistance, but the parallel resonance circuit build up by L & C. Because of the changing of impedance of LC, at the point of f0=
12?LC, the impedance get the apogee as a resistance performance with
the highest magnification. In this case, we can choose to amplify the very frequency signals. So, it is widely used as selected frequency amplifier in high and middle frequency environment.
Pic 1-1 Single-tuner resonant amplifier circuit
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D. Process
1、Get the modular G2 connected and the small high-frequency signal tuner amplifier parts JA1. Connect the +12V power supplier. 2、Transform K1 to right to make the LED on. 3、Adjust the standard point of the transistor.
Test to read the voltage of ejector of QA1 with the INA1 connected to ground. Adjust WA1 to make UEQ=2.25V. And then, read and notate the standard point. metrical VBQ VEQ VCQ VCEQ Whether Q1 working as amplifier depend on Vce Yes No Warrant: when Q1 is working as amplifier：VBEQ=VBQ-VEQ≈0.6V~0.7V，VCEQ equals to VCQ-VEQ
4、The frequency of circuit resonant f0
INA1 connects to signal of sine wave Ui with fs?10.700MHz and amplitude
V1P~P?20mV. Connect INB1 to oscillograph and fine-tuning CCA2 to make the graph on the oscillograph with the most amplitude. Draw down the wave graph. 5、Voltage magnification AV0
Based on process 4, the Ui is for input signal. Read out the quantity of Ui and the output signal Uo. So, the magnification can be calculated by Uo/Ui. 6、Band Δf0.7, Rectangular coefficient Kr0.1 and Q
Based on resonant state, change the input frequency with keeping the amplitude static. Read and note down the output voltage into the form below without the distortion ones.
Form 1-1 fS（MHz） Uo f0.1L f0.3L f0.5L f0.7L f0 f0.7H f0.5H f0.3H f0.1H Characteristics of amplitude-frequency Band： Δf0.7 = fH-fL
Q?
f0?f0.7；Rectangular coefficient：Kr0.1=
?f0.1 ?f0.7- 2 -
Pic. 1-2 Characteristics of amplitude-frequency
E. Requirements for the Report of Experiment 1. Finishing the experimental data;
2. Calculate DC points compare with experiment result;
3. Calculate Voltage gain when f0, bandwidth, Rectangular coefficient and Q according to form 1-2
4. Talk about the characteristics of single-tuner circuit resonant
F. Thinking
1.Talk about the characteristics of Single-tuner resonant amplifier circuit and RC-coupled amplifier
2.What effect does damping resistance R make to the gain?
3.What is the reason leading to unstable of high-frequency low signal tuner amplifier? How to make deal with self-incentive?
G．Words
单调谐回路谐振放大器: Single-tuner resonant amplifier
高频小信号调谐放大器: high-frequency low signal tuner amplifier 示波器: Oscillograph
选频放大器: selected frequency amplifier
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2nd Lesson: High-frequency resonant amplifier
A. Experiment aim
1、Understand principle of resonant power amplifier, effect of load impedance and voltage changing of encouraging signals.
2、Get mastery of characteristics of resonant power amplifier.
B. Apparatus
1、Oscilloscope one 2、Digital multimeter one 3、High-frequency experimentation case one
C. Experimental circuit principle
Resonant power amplifier uses selected frequency net as the load circuit. According to current amplifier angle range θ, we considered them as A, B,C, D 4 kinds. The smaller the angle, the more the larger efficiency η is. Kind A,θ=180,η no larger than 50%，when kind C with θ< 90o, η less or equal to 80%. A general as a power amplifier output power of the middle-class or smaller level at the end of the use of power amplifier, when general C amplifier is usually as a end-class to get greater power output and high efficiency. Picture 2-1 is one of the high-frequency amplifiers composed by two gear of amplifier.
Pic 2-1 high-frequency amplifier
The transistor VT1 composes general A amplifier, working the statue of lineal amplifier.
RB1 and RB2 are bias resistance at base with DC negative feedback RE1 and AC negative feedback RF1, to steady the point. The transistor VT2 composes general C amplifier, with θ=70o, base bias uses emitter current IEO that generates the voltageVBB on resistance of Re, with DC feedback 30Ω, AC feedback 10Ω, collector resonant circuit capacitance 82pF and load of 50Ω. The output uses transformer coupled output with middle tap for impedance matching.
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D. Process
Connect sending modular G1, according to high-frequency resonant amplifier in sending modular and connect the +12V power.
1、Switch K2 left and change WE1, to make voltage on emitter QE1 VE=2.2V. 2、Connect JE3 and JE6.
3、At INE1, input 10.700MHz carrier signal with VP-P=250mV. Change CCE1 and CCE2 to make the output wave max at ANTE1 from the Oscilloscope.
Details:
①．QE1 on collector, inching CCE1 to make the output max without distortion ②．QE2 on collector, inching CCE1 to make the output max without distortion
③．QE2 on ejector, the correct waveform is spires cosine pulse. You should decrease the rate if it concave. Note down the waveform and UA。 ④．Note down the waveform of ANTE1 4、Characteristics of load
After the 3rd process, change the load to make the resistance from 25Ω through 51Ω to 100Ω, with the circuit from owe-voltage through critical to pass-voltage on TTE1. In the circuit JE3，JE4 and JE5, the following resistances are 51Ω, 51Ω & 100Ω, so, R=25Ω（51Ω||51Ω）, that is, connect JE3，JE4 the same time. Note down the test digital below. Warrant： Po= （Uo* Uo）/8R fs=10.700MHz ，VP-P=UA R= 25Ω 51Ω 100Ω 5、Amplifier Characteristics：
①．After the 4th process, connect the JE3 & JE6 and note down the ejector voltage waveform on QE2.
②．Increase the input signal rate till the ejector on QE2 turn out to be concave, saying VT2 is in pass-voltage state. Note down the waveform.
③．Increase the input signal rate more; you can see the depth of the concave increasing.
Uo(Test) Po(Cal) E. Requirements for the Report of Experiment
1、Paint the pictures of current of three kinds of amplifier working 2、Paint the characteristics of load 3、Analyze the experience result
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