Tag: Oscillator Circuits

Back to Main Index of Book

Figure below shows a photodiode amplifier for measuring low levels of light. Best sensitivity and bandwidth are obtained with a trans-impedance amplifier, a current to voltage amplifier, instead of a conventional operational amplifier. The photodiode remains to reverse biased for lowest diode capacitance, hence wider bandwidth, and lower noise. The feedback resistor sets the “gain”,…

When someone mentions the word “computer,” a digital device is what usually comes to mind. Digital circuits represent numerical quantities in binary format: patterns of 1’s and 0’s represented by a multitude of transistor circuits operating in saturated or cutoff states. However, analog circuitry may also be used to represent numerical quantities and perform mathematical…

(a) Crystal radio. (b) Modulated RF at antenna. (c) Rectified RF at diode cathode, without C2 filter capacitor. (d) Demodulated audio to headphones.   An antenna ground system, tank circuit, peak detector, and headphones are the main components of a crystal radio seen in figure (a). The antenna absorbs transmitted radio signals (b) which flow…

Back to Main Index of Book

Phase shift oscillator. R1C1, R2C2, and R3C3 each provide 60° of phase shift.   The phase shift oscillator of the figure above produces a sine wave output in the audio frequency range. Resistive feedback from the collector would be negative feedback due to 180° phasing (base to collector phase inversion). However, the three 60° RC…

Note, Q3 and Q4 in the figure below are complementary, NPN and PNP respectively. This circuit works well for moderate power audio amplifiers. For an explanation of this circuit see “Directly coupled complementary-pair,”  Ch 4. Direct coupled complementary symmetry 3 w audio amplifier Back to Main Index of Book

There are three major kinds of power supplies: unregulated (also called brute force), linear regulated, and switching. The fourth type of power supply circuit called the ripple-regulated, is a hybrid between the “brute force” and “switching” designs, and merits a subsection to itself. Unregulated An unregulated power supply is the most rudimentary type, consisting of…

At the start of this book, we discussed static electricity and how it is created. This has a lot more significance than might be first assumed, as the control of static electricity plays a large part in modern electronics and other professions. An ElectroStatic Discharge event is when a static charge is bled off in…