The bipolar junction transistor is a current-controlled device, while the field-effect transistor (FET) is a voltage-controlled device. The field-effect transistor uses basically no input current. Instead, output current flow is controlled by a varying electric field, which is created through the application of a voltage. This is the origin of the term field effect. The […]
Operational amplifiers (op-amps) are analog circuit components that require power to operate. They are widely used in amplification and signal-conditioning circuits. The symbol for an op-amp is shown in Figure 1. The symbol is a triangle, with two leads drawn on one side of the triangle, and the third lead is drawn at the apex
Digital circuits are commonly available in two families: transistor-transistor logic (TTL) and complementary metal-oxide semiconductor (CMOS). There are other families, such as emitter-coupled logic (ECL), but they are not as widely used. TTL devices are based on the bipolar junction transistor technology, while CMOS devices are based on the FET transistor technology. Table 1 shows
Most commercial servo drives accept PWM and direction signals as input. Also, many servo drives produce a PWM output voltage signal to the load such as a motor coil instead of a linearly variable output voltage. A PWM signal is a square-wave signal of fixed amplitude and frequency, but the width of the on and
A very common application of transistors is to construct drivers to drive motors. One such circuit is the H-bridge driver circuit, which is commonly used to drive motors in both directions. The circuit looks like the letter ‘H’ in circuit schematics, so it is called an H-bridge. An H-bridge circuit is constructed using four switching
The 555 timer chip (such as the NE555 8-pin chip from Texas Instruments) is an integrated circuit that uses a transistor, resistors, flip-flops, comparators, and capacitors to produce a variety of clock signals, including a fixed pulse, a periodic signal, and a frequency dividing signal. The NE555 can operate over a wide voltage supply range
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A SCR (silicon-controlled rectifier) is a three-terminal semiconductor device that behaves like a diode but with an additional terminal. The additional terminal is called a gate, and when a small current flows into the gate, it allows a much larger current to flow from the anode to the cathode (provided that the voltage between the
Metal-oxide semiconductor field effect transistors (MOSFETs) are the other family of transistors that are commonly used. The MOSFET is based on the original field effect transistor (FET) that was introduced in the 1960s. Similar to the BJT family, they are also three terminal devices, but they have different names for the terminals, and they operate
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The oscilator, which typically varies in frequency from Hz to a few MHz, is an electronic device used to convert DC energy into AC energy with a high frequency. An external signal source, such as an amplifier, is not required for an oscillator. Oscillators typically come in two varieties: sinusoidal and non-sinusoidal. While non-sinusoidal oscillators
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Overview of PMOS When p-type dopants are utilized in the gate area (the channel), the transistor is known as a p-channel metal-oxide semiconductor (pMOS) or PMOSFET. The device activates when the gate receives a negative voltage. PMOS or pMOS also referred to as P-type metal-oxide-semiconductor logic, is a category of the digital circuit built employing