Tunnel Diode Parallel Amplifier Circuit: For operation as an amplifier, a tunnel diode must be biased to the center of its negative resistance region. Figure 21-17(a) shows the basic circuit of a Tunnel Diode Parallel Amplifier Circuit. Load resistor RL is connected in parallel with diode D1 and supplied with current from voltage source EB […]
Category: ELECTRONIC DEVICES
Tunnel Diode Operation and Characteristics
Tunnel Diode Operation and Characteristics: Tunnel Diode Operation – A tunnel diode (sometimes called an Esaki diode after its inventor, Leo Esaki) is a two-terminal negative resistance device that can be employed as an amplifier, an oscillator, or a switch. Recall from earlier topics that the width of the depletion region at a pn-junction depends […]
Thermistor Operation
Thermistor Operation: The word thermistor is a combination of thermal and resistor. A thermistor is a resistor with definite thermal characteristics. Most thermistors have a negative temperature coefficient (NTC), but positive temperature coefficient (PTC) devices are also available. Thermistor Operation are widely applied for measurement and control of temperature, liquid, level, gas flow, etc. Silicon […]
Voltage Variable Capacitors
Voltage Variable Capacitors: VVC Operation – Voltage Variable Capacitors diodes (VVCs) are also known as varicaps, varactors, and as tuning diodes. Basically, a Voltage Variable Capacitors is a reverse biased diode, and its capacitance is the junction capacitance. Recall that the width of the depletion region at a pn-junction depends upon the reverse bias voltage, […]
Optocoupler Circuit Operation
Optocoupler Circuit Operation: An Optocoupler Circuit Operation (optoelectronic coupler) is essentially a photo-transistor and an LED combined in one package. Figure 20-35(a) and (b) shows the typical circuit and terminal arrangement for one such device contained in a DIL plastic package. When current flows in the LED, the emitted light is directed to the phototransistor, […]
Photodarlington Working
Photodarlington Working: The Photodarlington Working shown in (Fig. 20-33) consists of a phototransistor connected in Darlington arrangement with another transistor. This device is capable of producing much higher output currents than a phototransistor, and so it has a greater sensitivity to illumination levels than either a phototransistor or a photodiode. With the additional transistor involved, […]
Phototransistors Working
Phototransistors Working: A Phototransistors Working is similar to an ordinary BJT except that its collector-base junction is constructed like a photodiode. Instead of a base current, the input to the transistor is in the form of illumination at the junction. Consider an ordinary BJT with its base terminal open-circuited, [Fig. 20-27(a)]. The collector-base leakage current […]
Solar Energy Conversion Diagram
Solar Energy Conversion Diagram: The Solar Energy Conversion Diagram, or solar energy converter, is essentially a large photodiode designed to operate solely as a photovoltaic device and to give as much output power as possible. To provide maximum output current, solar cell surface areas are much larger than those of signal photodiodes, Typical solar cell […]
Photodiode Operation and Characteristics
Photodiode Operation and Characteristics: Photodiode Operation – When a pn-Junction is reverse biased, a small reverse saturation current flows due to thermally generated holes and electrons being swept across the junction as minority charge carriers. Increasing the junction temperature generates more hole-electron pairs, and so the minority carrier (reverse) current is increased. The same effect […]
Photoconductive Cell Construction and Working
Photoconductive Cell Construction and Working: Photoconductive Cell Construction and Working – Light striking the surface of a material can provide sufficient energy to cause electrons within the material to break away from their atoms. Thus, free electrons and holes (charge carriers) are created within the material, and consequently its resistance is reduced. This is known […]
LED Seven Segment Display
LED Seven Segment Display: The arrangement of a LED Seven Segment Display is shown in Fig. 20-6(a). The actual LED devices are very small, so, to enlarge the lighted surface, solid plastic light pipes are often employed, as shown. Any desired numeral from 0 to 9 can be indicated by passing current through the appropriate […]
Light Units
Light Units: The total light energy output, or luminous flux (Φs), from a source can be measured in milliwatts (mW) or in lumens (1m), where 1 Im = 1.496 mW. The luminous intensity (Es) (also termed illuminance) of a Light Units source is defined as the luminous flux density per unit solid angle (or cone) […]
Programmable Unijunction Transistor
Programmable Unijunction Transistor: PUT Operation – The Programmable Unijunction Transistor (PUT) is actually an SCR-type device used to simulate a UJT. The interbase resistance (RBB) and the intrinsic standoff ratio (η) can be programmed to any desired values by selecting two resistors. This means that the device Ming voltage (the peak voltage VP) can also […]
UJT Circuit Diagram
UJT Circuit Diagram: UJT Circuit Diagram Operation : The Unijunction transistor (UJT) consists of a bar of lightly-doped n-type silicon with a block of p-type material on one side, [see Fig. 19-39(a)].The end terminals of the bar are identified as Base 1 (B1) and Base 2 (B2), and the p-type block is named the emitter […]
Silicon Bilateral Switch
Silicon Bilateral Switch: It might be convenient to think of a Silicon Bilateral Switch (SBS) as an SUS with a gate terminal, or as a low-current TRIAC. However, the SBS is not simply another four-layer device. Silicon bilateral switches are actually integrated circuits constructed of matched transistors, diodes, and resistors. This produces better parameter stability than […]
Silicon Unilateral Switch
Silicon Unilateral Switch: The Silicon Unilateral Switch (SUS), also known as a four layer diode and as a Schokley diode, can be treated as a low-current SCR without a gate terminal. Figure 19-30 shows the Silicon Unilateral Switch circuit symbol and typical forward characteristics. The device triggers into conduction when a forward switching voltage (VS) […]
TRIAC Control Circuit Diagram
TRIAC Control Circuit Diagram: A TRIAC Control Circuit Diagram that allows approximately 180° of phase control is shown in Fig. 19-27(a). The waveforms in Fig. 19-27(b) illustrate the circuit operation. With the TRIAC (Q1) off at the beginning of the supply voltage positive half-cycle, capacitor C1 is charged positively via resistors R1 and R2, as […]