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In order for the oscillator circuit to work properly, the amplifier circuit must be set to class A and the VCE voltage must be 1/2 VCC, to produce a sinusoidal wave that is not defective.
The resonator circuit installed must not interfere with the amplifier characteristics, as follows:
- By installing capacitors leading to the input and output points
- The function of C at the input and output is to suppress the DC current entering the network, so the installation of the resonator should not interfere with the amplifier.
- If the resonator is installed in series with the amplifier, it is called a series oscillator and if it is installed in parallel, it is called a parallel oscillator.
- The feedback circuit is taken from the resonator circuit with the largest signal return so that the oscillator amplifier can vibrate.
Class A Amplifier
From the image above, we get a comparison of resistance values:
- R1 : R2 = 10 : 1
- RC : RE = 5 : 1
- C : 10 nf
Concept of Current and Voltage
DC (Direct Current)
- Every time the value changes, it remains constant (the same)
- Does not have frequency
- Each has a current and is given resistance, then its value is pure or (resistive)
AC (Alternathing Current)
- Every time the time changes, the value changes / vibrates.
- Have frequency
- Every time there is a current and a load is applied, the resistance value is an impedance.
This concept is one that is often developed in oscillator techniques that function as filters, pay attention to the types of OSCILLATORS below:
Types of Oscillators
Holding high frequencies and passing low frequencies. The magnitude of the output voltage from this integrator circuit is determined by the formula:
Vo = - (1/RC) ʃ V1 . dt
Meanwhile, the magnitude of the cut off frequency is given by the equation:
Fc = 1/(2πRC)
If the position of R and C is reversed, the circuit changes into a differentiator (HPF/High Pass Filter) or upper pass filter, namely a filter that functions to hold low frequencies and pass high frequencies.
The magnitude of the output voltage is determined by the following equation:
Vo = - (RC) dVi /dt
While the cut off frequency is:
Fc = 1/(2πRC)
The following are the frequency response statistics:
Integrator
Differensiator
Voltage Comparator is a voltage comparison circuit on the input, namely an input compared to another input. The configuration of this circuit, uses open loop mode. The voltage comparison between the two inputs within a few minutes will drive the output voltage on the Op-Amp into saturation.
The output voltage will immediately saturate if the polarity of the input signal is different. If the voltage at the inverting input is more positive than the voltage at the non-inverting input, then the output voltage will swing to negative saturation (-Vsat), conversely if the inverting input voltage is more negative than the non-inverting input voltage, then the output voltage will swing to positive saturation (+Vsat) and when the inverting input and non-inverting input have the same amplitude and polarity then the output voltage will be equal to zero (0).