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 outp ...
s that have balanced inputs ''and'' outputs.
Methods
* using a unity gain
inverting amplifier
This article illustrates some typical operational amplifier applications. Operational amplifiers are optimised for use with negative feedback, and this article discusses only negative-feedback applications. When positive feedback is required, a c ...
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, thermionic 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 voltage, potential difference has been applied. It ...
implementations); a
transistor
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...
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 amplifier, amplifying vacuum tube (or ''thermionic valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated Electrical filament, filament or cathode, a control grid, grid ...
vacuum tube
A vacuum tube, electron tube, thermionic 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 voltage, potential difference has been applied. It ...
s or
FETs respectively) 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) 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 or common-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
In electrical engineering, a transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any coil of the transformer produces ...
with two equal secondary windings can be used (often with an amplifier stage to drive the primary).
Uses
* driving an amplifier in a
balanced
In telecommunications and professional audio, a balanced line or balanced signal pair is an electrical circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths, to ground, and to other c ...
topology, such as
push-pull or
H bridge
An 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 s ...
.
* driving balanced
transmission lines
In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmis ...
or balanced audio cables;
* supplying voltages in an
oscilloscope
An oscilloscope (formerly known as an oscillograph, informally scope or O-scope) is a type of electronic test instrument that graphically displays varying voltages of one or more signals as a function of time. Their main purpose is capturing i ...
to pairs of deflection plates in the
CRT
CRT or Crt most commonly refers to:
* Cathode-ray tube, a display
* Critical race theory, an academic framework of analysis
CRT may also refer to:
Law
* Charitable remainder trust, United States
* Civil Resolution Tribunal, Canada
* Columbia ...
;
* 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 it ...
s to approximate quadrature signals used in
SSB signal generation or old
decoders.
References
External links
Phase Splitters- Transistors Tutorial Part 2: "Bipolar Transistors"
*
Analog circuits
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