3Topics Covered in Chapter 29 Analog and Digital SignalsAmplifier GainCharacteristics of Amplifier CircuitsOscillators and Multivibrators
4Topics Covered in Chapter 29 (continued)ModulationDiode RectifiersTroubleshooting the DC Supply Voltage
5Types of SignalsAnalog signals have continuous variations in voltage or current level.Digital signals usually have only two levels.
6Digital and Analog Signals 2 levels levelsAnalog signalDigital signal
7AmplificationAn amplifier circuit increases the amplitude of a signal.The gain of an amplifier is the ratio of output signal level to input signal level.The voltage gain of an amplifier is given by: Av = output voltage/input voltageThe current gain of an amplifier is given by: Ai = output current/input current
8Amplification (gain) Av = output voltage/input voltage Ai = output current/input current
9Cascaded AmplifiersAmplifiers are said to be cascaded when the output of one amplifier is fed to the input of the next amplifier.The overall gain of cascaded amplifiers is equal to the product of the individual amplifier gain values.
10Cascade AmplifiersVOUTVINAV1AV2VOUT = AV1x AV2 x VIN
11Active Components in Amplifiers Active components include:TransistorsIntegrated circuitsActive components can increase signal levels.Active components require a power supply in addition to an input signal.
12Passive Components in Amplifiers Resistors are used to provide IR voltage drops in amplifier circuits.Capacitors are used for signal coupling and bypass circuits.Inductors are used as chokes and transformers.Capacitors and inductors are combined in resonant circuits.
14Oscillator CircuitsAn oscillator is an amplifier with positive feedback.No input signal is required.An oscillator generates an ac output when energized by a dc supply.
15RF Feedback Oscillators Tuned circuits determine the operating frequency.A Hartley oscillator uses a tapped coil as an ac voltage divider for feedback.A Colpitts oscillator uses a capacitive voltage divider for feedback.
17MultivibratorsA multivibrator produces an output voltage that alternates between a HIGH and LOW level.An astable multivibrator produces a continuous train of pulses.A bistable multivibrator is stable at the HIGH or LOW state, but can be triggered to the opposite state.
19ModulationModulation is the process of modifying one signal according to the variations of another signal at a lower frequency.Amplitude modulation (AM) varies the amplitude of the RF carrier signal.Frequency modulation (FM) varies the frequency of the RF carrier signal.
20Amplitude Modulation X 400 Hz1 MHzXThe instantaneous amplitude of the 1 MHz carrier is controlled by the 400 Hz input signal.
21Frequency Modulation VCO 400 HzVCOThe instantaneous frequency of the voltage controlled oscillator (VCO) is determined by the 400 Hz input signal.
22DC Power SuppliesA dc power supply converts 60 Hz ac power to a dc level.The dc level from a power supply is needed as a source of power for amplifiers, oscillators, and other types of active circuits.A half-wave power supply uses only one-half of each ac waveform.A full-wave rectifier uses both alternations the input ac waveform.