A phase splitter is a device that separates a signal into multiple phases (or polarities).
The term is most often applied to amplifiers that produce two "balanced" voltage outputs: of equal amplitude but opposite polarity (i.e. 180 degrees phase difference), but sometimes is used to refer to the generation of
quadrature signals (i.e. differing by 90 degrees). The term is not used for
logic circuits producing complementary outputs, nor applied to
differential amplifier
A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs V_\text^- and V_\text^+ and one outpu ...
s that have balanced inputs ''and'' outputs.
Methods
* using a unity gain
inverting amplifier
This article illustrates some typical operational amplifier applications. A non-ideal operational amplifier's equivalent circuit has a finite input impedance, a non-zero output impedance, and a finite gain. A real op-amp has a number of non-ideal f ...
to provide an inverted copy of its input signal;
* a split-load amplifier (also known as a "cathodyne" or "concertina phase splitter", especially in the context of
vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
The type known as ...
implementations); a
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
implementation is shown in the diagram;
* a
differential pair amplifier can form a phase splitter in two ways:
** if the shared emitter (or cathode or source, for
triode
A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's ...
s or
FETs) connection is fed from something approximating a constant current sink (for example, a relatively large value resistor with a significant voltage drop, i.e. a
long-tailed pair
A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs V_\text^- and V_\text^+ and one outp ...
) then only one input (base, grid or gate) need be driven with signal; the shared connection will vary in voltage with half the amplitude of the input, becoming an input to the second device (which acts as a common-base, or common-grid/gate amplifier). The sum of the currents in each of the collectors (or anodes or drains) will be almost constant, hence an increase in one will be matched by an equal decrease in the other, giving rise to equal, but opposite phase, voltages on the outputs. This technique was first described by O.H. Schmitt.
** if the shared emitter (or cathode or source) resistor is relatively small, total current will vary with signal, and the signal will not be evenly split across both outputs, so a fraction of the first device's output will have to be fed to the second device's base or grid or gate to balance the amplitudes at the two outputs. Effectively, the second device is acting now as an inverting unity-gain amplifier.
* A
transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
with two equal secondary windings can be used (often with an amplifier stage to drive the primary).
Uses
* driving an amplifier in a
balanced topology, such as
push-pull or
H bridge A H-bridge is an electronic circuit that switches the polarity of a voltage applied to a load. These circuits are often used in robotics and other applications to allow DC motors to run forwards or backwards.
The name is derived from its common sch ...
.
* driving balanced
transmission lines or balanced audio cables;
* supplying voltages in an
oscilloscope
An oscilloscope (informally a scope) is a type of electronic test instrument that graphically displays varying electrical voltages as a two-dimensional plot of one or more signals as a function of time. The main purposes are to display repetiti ...
to pairs of deflection plates in the
CRT;
* producing anti-phase signals used in some filter designs, such as
all-pass filter
An all-pass filter is a signal processing filter that passes all frequencies equally in gain, but changes the phase relationship among various frequencies. Most types of filter reduce the amplitude (i.e. the magnitude) of the signal applied to i ...
s to approximate quadrature signals used in
SSB signal generation or old
quadraphonic
Quadraphonic (or quadrophonic and sometimes quadrasonic) sound – equivalent to what is now called 4.0 surround sound – uses four audio channels in which speakers are positioned at the four corners of a listening space. The system allows for t ...
decoders.
References
External links
Phase Splitters- Transistors Tutorial Part 2: "Bipolar Transistors"
*
Analog circuits
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