The transistor forms the main electronic component in all transistor circuits. You can obtain the electronic components in discrete form. Also, they could be integrated within an IC.
The manufacturing of these transistors come in different formats and they could be obtained so as to achieve different roles including small and high power as well as switching, RF, and audio.
What Does a Transistor Circuit Diagram Mean?
Transistor circuits are usually found at the center of the electronic circuits’ designs of today. Though integrated circuits are useful for so many circuits, the usefulness of the transistor circuit diagram in different areas cannot be overemphasized.
Though making use of discrete electronic components having transistors makes use of more components, tailoring the circuit to offer the required functionality is possible. Accordingly, circuits that make use of discrete transistors as well as more electrical components still form the core of electronic circuit designs.
What this means is that, having a good understanding of the transistor circuit diagram is very important because it would both allow the design of the main transistor circuits, and provide better understanding when operating integrated circuits based on the bipolar transistor technologies.
What are Transistors?
Transistors can be described as a semiconductor device, which is useful for the conduction and insulation of voltage or electric current. Basically, the transistor serves as an amplifier and a switch. Explained in simple terms, the transistor serves as a miniature device, which is useful in controlling or regulating the electronic signal flow.
Furthermore, transistors form a major component in the majority of electronic devices present today. Developed by three Physicists from America, William Shockley, Walter Brattain, and John Bardeen in 1947, this transistor is viewed among the most significant inventions in science’s history.
Typical transistors are made of three main semiconductor material layers or terminals that aid in connecting to the external circuits as well as carry the current. The current or voltage that is applied to any of the pairs of a transistor’s terminals helps in controlling the current via other terminal pairs. A transistor comes with three terminals. These include:
- Emitter: which is the transistor’s negative lead
- Collector: Which is the transistor’s positive lead
- Base: This helps in activating the transistor
Transistor Types
Transistors come in two major types and these are based on the way they are utilized in circuits. Let’s consider them.
Bipolar Junction Transistors
Bipolar junction transistors feature three terminals. These include collector, emitter, and base. An extremely small quantity of current passing in-between the emitter and the base can control the larger current flow in-between the emitter terminal and collector.
Field Effect Transistors
For the field effect transistors, there are three terminals, which are Drain, Source, and Gate. The gate terminal’s voltage can control the current found between the drain and the source. Field effect transistors are unipolar transistors whereby P-channel FETs or N-channel FETs are utilized for conduction purposes. Their applications include analogue switches, buffer amplifiers, low noise amplifiers.
How Does a Transistor Work?
Transistors serve as a gate or switch for an electronic signal, opening as well as closing of an electronic gate as many times every second. It makes sure that the circuit stays on whenever there is a flow of current and then switches off whenever it isn’t.
In addition, transistors are utilized in different complex switching circuits which are made up of all the telecommunication systems of today. Also, circuits provide extremely high switching speeds like at least hundreds gigahertz than the 100 billion on and off cycles every second.
Furthermore, you can combine transistors to form logic gates, which helps in the comparison of many input currents so as to offer different outputs. Computers having logic gates have the ability to make easy decisions making use of Boolean algebra. The techniques form the basis of today’s computer and computing programs.
Also, transistors play a significant role in the amplification of electronic signals. Take for instance, in the radio applications, such as FM receiver, whereby the electric signal received might be weak as a result of disturbances, the amplification becomes necessary to deliver audible output. In addition, these transistors offer the amplification through increase of the strength of the signal.
Design Parameters of the Transistor Circuit Diagram
Before you handle the circuit design of transistor circuits, defining the circuit’s requirements is necessary. Some important parameters linked to the transistor circuit diagram include.
Voltage gain
This is usually a major requirement for electronic circuit designs. The circuit’s voltage gain is a voltage increase from the circuit’s input into its output. Explaining mathematically, the gain in voltage is the quotient between the output voltage and input voltage. Also, voltage gain can be viewed as one of the main purposes of many circuits. This is because it helps to enable the size.
Current Gain
A circuit’s current gain is also important, most especially whenever the circuit will be driving a load with low impedance. Usually circuits without any voltage gain and just current gain are required to enable relatively-high impedance output circuits to drive a second circuit, which has lower impedance.
So many examples are applicable here. RF oscillators usually require the buffer stage so as to make sure that oscillator circuits are not unduly loaded, however the output is required to help in deriving the remaining circuits. The gain in current is also utilized in the power supply circuit whereby the voltage regulator’s series pass elements have to provide high current levels, however making use of the low voltage current reference. Other examples whereby current gain is necessary and required.
Just like the voltage gain, a circuit’s current gain draws a comparison between both the output and input levels. However, this happens in terms of the current. Furthermore, current gain equals the output current and then divided by input current.
The Input Impedance
A transistor circuit’s input impedance always plays a significant role. It helps in the determination of the loading on the initial stage. Also, it is important for RF circuits whereby the impedance matching is a very important parameter.
For many designs of electric circuits, high input impedance is usually desirable because the initial stage won’t be unduly loaded. If the transistor circuit’s input impedance is extremely low, then the initial one would be loaded. This then reduces the level of signal and thereby causes some distortion in some scenarios. In addition, the configuration of the transistor stage in providing the appropriate input impedance forms a major element of the process of electronic circuit designs.
Design Process of the Transistor Circuit Diagram
There are different stages involved in the design process of the transistor circuit diagram. They are taken in the logical order, however there are some revisiting of these stages in order to optimize the electronic components’ values in order to offer the overall performance required.
Determine the requirements
A very important phase is to determine the real requirements, as well as getting it correctly would mean that the circuit’s concept will not change later on.
Determine the topology and function of the circuit
Immediately we have settled the requirements for the full electronics device, it becomes important to decide on the actual transistor circuits. For instance, many oscillator amplifiers, circuits are available for the transistors and it is possible to choose the best type for that specific requirement. Also, this defines the true circuit topology.
For example, the utilization of common base, common collector, common emitter, but if it isn’t, it could be a part of the general decision making during this period. This is because the loading on the output impedance, gain, oscillators, and others could be considered during this period.
Setting up the bias conditions
For all circuits, one important feature of an electronic circuit design involves ensuring the labels of bias for all active devices. For this reason, the bipolar transistors could be correctly set. If there’s an incorrect bias, this transistor circuit wouldn’t function.
The determination of the electronic components’ value (majorly the resistors), which sets the bias is one important stage of the transistor circuit diagram design.
Determining the values of the functional electronic components
Coupled with setting the conditions of the bias, other values of the electronic components to offer the appropriate circuit functionality has to be determined. This phase of transistor circuit diagram design will proceed with the setting of the bias conditions, as one value will have an effect on the other value.
Conclusion
It is clear that the main electronic component in all transistor circuits is the transistor. You can obtain these components discretely or they might be within the integrated circuits.
