- A very popular local oscillator circuit that is mostly used in radio receivers is the Hartley Oscillator circuit. The constructional details and operation of a Hartley oscillator are as discussed below.
- 5.1 YIG oscillators with integrated driver There are also types of equipment that already incorporate the YIG driver. 13 and 14 show oscillators like this. These are then usually tuned with a tuning voltage of between 0 and 10V. A connection diagram should acquired for these types, since no rules are applicable here. Finally, I’d like.
Tuned Oscillators (Radio Frequency Oscillators) 17 Tuned oscillator is a circuit that generates a radio frequency output by using LC tuned (resonant) circuit. Because of high frequencies, small inductance can be used for the radio frequency of oscillation. Tuned-input and tuned-output Oscillator tuned-output tuned-input feedback coupling ci RF. Oscillators Oscillators 6 Figure 6-1: PIC32 Family Oscillator System Block Diagram Note 1: A series resistor, RS, may be required for AT strip cut crystals or to eliminate clipping. Alternatively, to increase oscillator circuit gain, add a parallel resistor, RP, with a value of 1 M.
An oscillator is one kind of an electronic circuit that generates an oscillating, periodic electronic signal such as a sine wave (or) a square wave. The main function of an oscillator is to convert DC (direct current) from a power supply to an AC (alternating current) signal. These are widely used in several electronic devices. General examples of signals produced by oscillators comprise signals broadcast by the transmitters of a TV and a radio transmitter, CLK signals that control the quartz clocks and computers. The sounds generated by video games and electronic beepers. The oscillator is often characterized by the output signal’s frequency. Oscillators are mainly designed to generate an output of high-power AC from a direct current supply that is frequently called inverters.
The different types of oscillators have the same functions, that they generate continuous undamped o/p. But, the main difference between the oscillators lies in the method by the energy which is supplied to the tank circuit to meet up the losses. The common types of transistor oscillators mainly include tuned collector oscillator, Colpitt’s oscillator, Hartley, phase shift, Wein bridge and a crystal oscillator
What is a Tuned Collector Oscillator ?
The tuned collector oscillator is one kind of transistor LC oscillator where the tank circuit comprises of a capacitor and a transformer, that is connected to the collector terminal of the transistor. The tuned collector oscillator circuit is the simplest & the basic kind of LC oscillators. The tank circuit connected in the collector circuit performs like a simple resistive load at resonance and decides the oscillator frequency. The general applications of this circuit include signal generators,RF oscillator circuits, frequency demodulators, mixers, etc. The circuit diagram and working of a tuned collector oscillator are discussed and shown in the following below.
Tuned Collector Oscillator Circuit
The circuit diagram of the tuned collector oscillator is shown below. For the transistor, the resistors R1, R2 form a voltage divider bias. The emitter resistor ‘Re’ is which is intended for thermal stability. It also stops the transistor’s collector current and the emitter bypass capacitor ‘Ce’. The main role of ‘Ce’ is to avoid improved oscillations. If the emitter bypass capacitor is not there, the amplified AC oscillations will fall across emitter resistor ‘Re’ and will add on to the ‘Vbe‘ base-emitter voltage of the transistor. And after this, this will change the conditions of DC biasing. In the circuit below, primary of the transformer L1 and capacitor C1 shapes the tank circuit.
Tuned Collector Oscillator Circuit Working
When the power supply is turned ON, the transistor gets the current and starts conducting. The ‘C1’ capacitor starts charging. When the C1 capacitor gets the charge, then the charge starts discharging through the primary coil L1 of the transformer.
When the capacitor C1 is fully discharged, the energy in the capacitor as the electrostatic field will be stirred to the inductor as the electromagnetic field. Now there will be no more voltage across the capacitor to maintain the current through the primary coil in the transformer starts to collapse. In order to resist this, the L1 coil generates a back emf which may charge the capacitor again. Then capacitor ‘C1’ discharges through the L1 coil and the series is constant. This charging & discharging sets up a sequence of oscillations in the tank circuit.
Jlr mongoose sdd v145 v146 v148 faq auto diagnostic tool independent repair. Reflector license key. The oscillations generated in the tank circuit is fed back to the base terminal of the Q1 transistor by the minor coil by inductive coupling. The quantity of feedback can be regulated by changing the ratio twists of the transformer.
The direction of the secondary winding coil ‘L2’ is in such a way that the voltage across it will be 180° phase opposite to that of the voltage across the primary (L1). Therefore the feedback circuit generates 180° of phase shift and the Q1 transistor produces 180° of phase shift of another.As a result the total phase shift is acquired between input & output. It is an extremely required condition for positive feedback and continued oscillations.
The collector current (CC) of the transistor balances the lost energy in the tank circuit. This can be done by adopting a little amount of voltage from the tank circuit, strengthening it and applying it back to the circuit. The Capacitor ‘C1’ can be made variable in the applications of variable frequency.
In the tank circuit, the frequency of oscillations can be expressed using the following equation.
F = 1/ 2π√[(L1C1)]
In the above equation, ‘F’-denotes the frequency of oscillation and L1-is the inductance of the transformer’s primary coil and C1-is the capacitance.
Application of Tuned Collector Oscillator Circuit
The applications of tuned collector oscillator involves in the local oscillator of a radio. All transformers introduce 180º of a phase shift between primary & secondary.
Electronics receiver principles make use of an LC tuned circuit with the following
C1 = 300 pF and L1 = 58.6 μH
Frequency of oscillations can be calculated by the following procedure
C1 = 300 pF
= 300 × 10−12 F
L1 = 58.6 μH
= 58.6 × 10−6 H
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Frequency of oscillations, f = 1/ 2π√L1C1
f = 1/ 2π √58.6 × 10−6 x300 × 10−12 Hz
1199 × 103 Hz
= 1199 kHz
Thus, this is all about Tuned collector oscillator circuit working and applications. We hope that you have got a better understanding of this concept. Furthermore, any doubts regarding this concept or to implement the electrical and electronics projects, please give your valuable suggestions by commenting in the comment section below.Here is a question for you, what is the main function of an oscillator?
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A very popular local oscillator circuit that is mostly used in radio receivers is the Hartley Oscillator circuit. The constructional details and operation of a Hartley oscillator are as discussed below. Mac os x el capitan online emulator online.
Construction
In the circuit diagram of a Hartley oscillator shown below, the resistors R1, R2 and Re provide necessary bias condition for the circuit. The capacitor Ce provides a.c. ground thereby providing any signal degeneration. This also provides temperature stabilization.
The capacitors Cc and Cb are employed to block d.c. and to provide an a.c. path. The radio frequency choke (R.F.C) offers very high impedance to high frequency currents which means it shorts for d.c. and opens for a.c. Hence it provides d.c. load for collector and keeps a.c. currents out of d.c. supply source
Tank Circuit
The frequency determining network is a parallel resonant circuit which consists of the inductors L1 and L2 along with a variable capacitor C. The junction of L1 and L2 are earthed. The coil L1 has its one end connected to base via Cc and the other to emitter via Ce. So, L2 is in the output circuit. Both the coils L1 and L2 are inductively coupled and together form an Auto-transformer.
The following circuit diagram shows the arrangement of a Hartley oscillator. The tank circuit is shunt fed in this circuit. It can also be a series-fed.
Operation
When the collector supply is given, a transient current is produced in the oscillatory or tank circuit. The oscillatory current in the tank circuit produces a.c. voltage across L1.
The auto-transformer made by the inductive coupling of L1 and L2 helps in determining the frequency and establishes the feedback. As the CE configured transistor provides 180o phase shift, another 180o phase shift is provided by the transformer, which makes 360o phase shift between the input and output voltages.
This makes the feedback positive which is essential for the condition of oscillations. When the loop gain |βA| of the amplifier is greater than one, oscillations are sustained in the circuit.
Frequency
The equation for frequency of Hartley oscillator is given as
$$f = frac{1}{2 pi sqrt{L_T C}}$$
$$L_T = L_1 + L_2 + 2M$$
Here, LT is the total cumulatively coupled inductance; L1 and L2 represent inductances of 1st and 2nd coils; and M represents mutual inductance.
Mutual inductance is calculated when two windings are considered.
Advantages
The advantages of Hartley oscillator are
Instead of using a large transformer, a single coil can be used as an auto-transformer.
Frequency can be varied by employing either a variable capacitor or a variable inductor.
Less number of components are sufficient.
The amplitude of the output remains constant over a fixed frequency range.
Disadvantages
The disadvantages of Hartley oscillator are
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- It cannot be a low frequency oscillator.
- Harmonic distortions are present.
Applications
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The applications of Hartley oscillator are
- It is used to produce a sinewave of desired frequency.
- Mostly used as a local oscillator in radio receivers.
- It is also used as R.F. Oscillator.