Today’s electronic devices are made up of a wide variety of components. Some, like resistors and capacitors, are simple and passive, while others, such as advanced central processing unit (CPU) chips, are extremely complex and can contain over 20 billion transistors. In this lab, we introduce some simple components and some equipment that can be used to generate and characterize electronic signals in the forms of voltages and currents.
To introduce resistors, capacitors and inductors as examples of passive components. To introduce diodes and transistors as simple semiconductor components, and an operational amplifier (op-amp) as an example of an integrated circuit (IC). To introduce the Analog Devices M1K and PixelPulse2 application software. Following completion of this lab you should be familiar with the parts in the ADALP2000 Analog Parts Kit, be able to give basic descriptions of passive components, diodes, transistors, and op-amps, understand the basics of resistor and capacitor codes, and understand the basic operation of the M1K and PixelPulse application software.
A detailed list of the contents of the ADALP2000 Analog Parts Kit can be found here.
The components introduced in this lab will be used in the following labs to construct circuits that increase in complexity as the labs go on. The first of the subsequent labs uses two of the passive elements – resistors and capacitors – in ways that help illustrate how these elements behave in circuits.
Resistors (R) have the units of ohms (Ω), and control the instantaneous relationship between voltage (V) and current (I) according to Ohm’s law, V = I*R. Capacitors store electric charge, allow more current to flow as the signal frequency increases, and exhibit a phase shift between voltage and current in which the sinusoidal current leads the voltage by 90 degrees, or equivalently, the sinusoidal voltage lags the current by 90 degrees. Inductors behave in an opposite fashion. Inductors store energy in a magnetic field, allow less current to flow as the signal frequency increases, and exhibit a phase shift between voltage and current in which the sinusoidal voltage leads the current by 90 degrees, or equivalently, the sinusoidal current lags the voltage by 90 degrees. Resistors, capacitors, and inductors do not add any energy to a circuit, and therefore cannot be used to amplify the power of a signal.
Diodes are the simplest of semiconductor devices and allow current flow in only one direction. The original diodes were electronic tubes, constructed of a filament that emitted electrons and a metal plate that collected the electrons. In these diodes, the electrons can only flow from the filament to the plate when the plate is biased at a positive voltage that attracts the negatively-charged electrons. Modern diodes use a semiconductor ‘pn junction” to obtain the same result. Diodes are often used as switches, and to convert alternating current (AC) to direct current (DC).
Transistors have three terminals in most cases, and are the simplest semiconductor devices that are capable of amplifying the power of a signal. This is accomplished by applying the signal to be amplified to the transistor input terminal, and using the input signal to control the power from an external power supply according to the input signal. The signal with increased power is available at the output terminal. The transistor output is therefore a replica of the input signal with increased voltage amplitude, current amplitude, or both. The third terminal is generally connected to a reference voltage.
Op-amps are examples of ICs that are most often used in negative feedback configurations to provide signal amplification that is of better quality than can be obtained with a single transistor. In the fourth lab, an op-amp is combined with a 2N3904 transistor to provide signal voltage amplification and current amplification to drive a loudspeaker. The op-amp provides the voltage gain and the transistor, placed inside the negative feedback loop to provide the best performance, provides the current gain.
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