Analog circuits

Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.

The number of different analog circuits so far devised is huge, especially because a ‘circuit’ can be defined as anything from a single component, to systems containing thousands of components.

Here the thyristor explanation form wikipedia:

The thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current pulse, and continue to conduct for as long as they are forward biased (that is, as long as the voltage across the device has not reversed).

Some sources define silicon controlled rectifiers and thyristors as synonymous.

The Thyristor’s Function

The thyristor is a four-layer semiconducting device, with each layer consisting of alternately N-type or P-type material, for example P-N-P-N. The main terminals, labeled anode and cathode, are across the full four layers, and the control terminal, called the gate, is attached to p-type material near to the cathode. (A variant called an SCS—Silicon Controlled Switch—brings all four layers out to terminals.) The operation of a thyristor can be understood in terms of a pair of tightly coupled bipolar junction transistors, arranged to cause the self-latching action:

Thyristors have three states:

1. Reverse blocking mode — Voltage is applied in the direction that would be blocked by a diode
2. Forward blocking mode — Voltage is applied in the direction that would cause a diode to conduct, but the thyristor has not yet been triggered into conduction
3. Forward conducting mode — The thyristor has been triggered into conduction and will remain conducting until the forward current drops below a threshold value known as the “holding current”

This is an LED pulse effect circuit. The effect result of this circuit is that the LED goes from off state, lights up gradually, then dims gradually.

This operation mode is obtained by a triangular wave generator formed by two op-amps contained in a very cheap 8 pin DIL case IC. Q1 ensures current buffering, in order to obtain a better load drive. R4 and C1 are the timing components: using the values shown in the parts list, the total period is about 4 seconds.

R1,R2 _________4K7 ohm
R3    _________22K ohm
R4    _________2M2 ohm  (See Notes)
R5    _________10K ohm
R6    _________47R ohm  (See Notes)
C1    _________1µF/ 63V Polyester Capacitor
D1    _________5mm. LED (See Notes)
IC1   _________LM358  Low Power Dual Op-amp
Q1    _________BC337  NPN Transistor

Wanna to build an inverter circuit..? This is an ordinary transistorised inverter circuit capable of driving medium loads of the order of 40 to 60 watts using battery of 12V, 15 Ah or higher capacity. This inverter will convert 12V DC input to become 230V AC in output.

Transistors T1 and T2 (BC548) form a 50Hz multivibrator. For obtaining correct frequency, the values of resistors R3 and R4 may have to be changed after testing. The complementary outputs from collectors of transistors T1 and T2 are given to PNP darlington driver stages formed by transistor pairs T3-T4 and T6-T7 (utilising transistors BD140 and 2N6107).

This is very simple FM Radio receiver with only use 1 transistor.

Not only simple and easy to build, this circuit also inexpensive. You can build this circuit with low risk.