Slopes are expressed in either dB/decade or dB/octave. An octave represents a two-fold increase or decrease in frequency. The actual response will approach straight lines called asymptotes.ġ1 Bode Plots A decade represents a tenfold increase or decrease in frequency. The ordinate will be the gain expressed in dB. The abscissa will be the frequency on a logarithmic scale. At cutoff the voltage gain is -3dB and the phase angle is -45°.ġ0 Bode Plots A Bode plot is a straight-line approximation of the frequency response of a circuit. The cutoff frequency occurs when the gain drops to of the maximum gain. Common types of filters are low-pass, high-pass, band-pass, and band-reject filters.ĩ Low-Pass Filter A low-pass filter has a greater gain at low frequencies at higher frequencies the gain decreases. Any circuit which passes a particular range of frequencies is called a filter circuit. If the circuit contains capacitors or inductors, the transfer function will be frequency dependent.Ĩ Transfer Functions To examine the operation of a circuit over a wide range of frequencies, we draw a frequency response curve. The phase angle, , represents the phase shift between the input and output voltage phasors. The amplitude of the transfer function is the voltage gain. AT(dB) = A1(dB) + A2(dB) + A3(dB)ħ Transfer Functions The transfer function is the ratio of the output voltage phasor to the input voltage phasor for any frequency. AT = A1A2A3 If the gains are expressed in decibels (which are logarithmic), then gains will add instead of multiplying.

Because the bel is such a large unit, the decibel is often used.ĥ The Decibel To express voltage gain in decibels:Ħ Multistage Systems To find the total gain of a system having more than one stage, each with a gain of An, multiply the gains together.

Since gains may be very large or very small, it may be inconvenient to express the gain as a simple ratio.Ĥ The Decibel The bel is a logarithmic unit that represents a tenfold increase or decrease in power. Any circuit in which the output signal power is less than the input signal power is called an attenuator. Voltage gain is the ratio of output signal voltage to input signal voltage.ģ Gain Any circuit in which the output signal power is greater than the input signal power is referred to as an amplifier. Presentation on theme: 'Filters and the Bode Plot'- Presentation transcript:Ģ Gain Power gain is the ratio of output signal power to input signal power.

Multisim bode plot voltage gain