The V page
- See Voltage Controled Amplifier.
- See Voltage Controled Filter.
- See Voltage Controled Oscillator
- Voltage Controled Amplifier
- An device which acts like an linear amplifier
but for which the gain may be changed with
an applied control voltage.
It is normally an 2-quadrant multiplier where the input signal is
allowed to vary in both the positive and negative range.
The control voltage is normally either linearly or exponentially
dependent to the gain.
The VCA can be realised in numerous ways in which OTA
and Gilbert cells are common.
The VCA is related to ringmodulators.
- Voltage Controled Filter
- An device which act like an line filter but for which the filter
characteristics with one or more applied control voltage.
The control voltage will normally follow an exponential frequency behaviour
which normally is adjustable. There exists those VCFs which will react with
linearly frequency with applied voltage. Some filters will allow for
voltage control over the filters Q value, and some filters may even
allow for voltage control over filter type (lowpass, bandpass, highpass)
- Voltage Controled Oscillator
- An device which will generate waveforms. The frequency of these
waveforms can be controled with an applied control voltage. Normally
is the frequency changed exponentially, but some change linearly with
the control voltage. Some VCOs may allow for smaller linear
modulations as well as for the exponential modulation. Usually is
there a coarse tuning knob and sometimes also a fine tuning knob. Some
VCOs have a rotary switch to select which base octave the VCO should
be tuned to where as others may be widely sweept. VCOs may have
diffrent waveforms. Common waveforms is square,
PWM, triangle and
Some VCOs will also have sine waveform.
The PWM waveform migth have an additional
input for CV controlable
pulse width but some VCOs only allow for knob controled pulse width.
Some VCOs migth be synced to an applied
signal (often from a diffrent VCO), this is a way to lock the
waveforms to each other so that they will at have a common phase at
the sync time.
Some VCOs migth be PLL locked to an applied
signal, this way they will track the frequency of that signal.
VCOs typhically have problems with frequency tracking, frequency range
and temperature stabillity of it's frequency.
(C) 1997, 1998, 1999
Magnus Danielson <cfmd at bredband dot net>