Tuesday, April 29, 2014

RF Power Amplifiers

RF Power Amplifiers For Rent

Microwave Power Amplifier – Solid State Amp

An electronic amplifier, amplifier, or (informally) amp is an electronic device that increases the power of a signal. It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude. In this sense, an amplifier modulates the output of the power supply.

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There are four basic types of electronic amplifier: the voltage amplifier, the current amplifier, the transconductance amplifier, and the transresistance amplifier. A further distinction is whether the output is a linear or exponential representation of the input. Amplifiers can also be categorized by their physical placement in the signal chain.

Amplifier quality is characterized by a list of specifications that includes:

Gain, the ratio between the magnitude of output and input signals
Bandwidth, the width of the useful frequency range
Efficiency, the ratio between the power of the output and total power consumption
Linearity, the degree of proportionality between input and output
Noise, a measure of undesired noise mixed into the output
Output dynamic range, the ratio of the largest and the smallest useful output levels
Slew rate, the maximum rate of change of the output
Rise time, settling time, ringing and overshoot that characterize the step response
Stability, the ability to avoid self-oscillation

Amplifier types

Amplifiers are described according to their input and output properties. They exhibit the property of gain, or multiplication factor that relates the magnitude of the output signal to the input signal. The gain may be specified as the ratio of output voltage to input voltage (voltage gain), output power to input power (power gain), or some combination of current, voltage, and power. In many cases, with input and output in the same unit, gain is unitless (though often expressed in decibels (dB)).

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The four basic types of amplifiers are as follows:

Voltage amplifier – This is the most common type of amplifier. An input voltage is amplified to a larger output voltage. The amplifier’s input impedance is high and the output impedance is low.
Current amplifier – This amplifier changes an input current to a larger output current. The amplifier’s input impedance is low and the output impedance is high.
Transconductance amplifier – This amplifier responds to a changing input voltage by delivering a related changing output current.
Transresistance amplifier – This amplifier responds to a changing input current by delivering a related changing output voltage. Other names for the device are transimpedance amplifier and current-to-voltage converter.

In practice the power gain of an amplifier will depend on the source and load impedances used as well as the inherent voltage/current gain; while an RF amplifier may have its impedances optimized for power transfer, audio and instrumentation amplifiers are normally designed with their input and output impedances optimized for least loading and highest signal integrity. An amplifier that is said to have a gain of 20 dB might have a voltage gain of ten times and an available power gain of much more than 20 dB (power ratio of 100), yet actually be delivering a much lower power gain if, for example, the input is from a 600 ohm microphone and the output is connected to a 47 kilohm input socket for a power amplifier.

In most cases an amplifier will be linear; that is, the gain is constant for any normal level of input and output signal. If the gain is not linear, e.g., clipping of the signal, the output signal will be distorted. There are however cases where variable gain is useful. Exponential gain amplifiers are used in certain signal processing applications.

There are many differing types of electronic amplifiers used in areas such as: radio and television transmitters and receivers, high-fidelity (“hi-fi”) stereo equipment, microcomputers and other digital equipment, and guitar and other instrument amplifiers. The essential components include active devices, such as vacuum tubes or transistors. A brief introduction to the many types of electronic amplifiers follows.

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Power amplifier

The term power amplifier is a relative term with respect to the amount of power delivered to the load and/or provided by the power supply circuit. In general the power amplifier is the last ‘amplifier’ or actual circuit in a signal chain (the output stage) and is the amplifier stage that requires attention to power efficiency. Efficiency considerations lead to the various classes of power amplifier based on the biasing of the output transistors or tubes: see power amplifier classes.

Power amplifiers by application

Audio power amplifiers
RF power amplifier, such as for transmitter final stages (see also: Linear amplifier).
Servo motor controllers, where linearity is not important.
Piezoelectric audio amplifier includes a DC-to-DC converter to generate the high voltage output required to drive piezoelectric speakers.

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Agilent Spectrum Analyzer

Tektronix Logic Analyzer – Optical Spectrum

A logic analyzer is an electronic instrument that captures and displays multiple signals from a digital system or digital circuit. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or may correlate assembly with source-level software. Logic Analyzers have advanced triggering capabilities, and are useful when a user needs to see the timing relationships between many signals in a digital system

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Many digital designs, including those of ICs, are simulated to detect defects before the unit is constructed. The simulation usually provides logic analysis displays. Often, complex discrete logic is verified by simulating inputs and testing outputs using boundary scan. Logic analyzers can uncover hardware defects that are not found in simulation. These problems are typically too difficult to model in simulation, or too time consuming to simulate and often cross.

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Logic Analyzers
Noise Figure Analyzers
Network Analyzers
Optical Spectrum Analyzers
Serial Data Analyzers
Spectrum Analyzers
Signal Analyzers

A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals. The input signal a spectrum analyzer measures is electrical, however, spectral compositions of other signals, such as acoustic pressure waves and optical light waves, can be considered through the use of an appropriate transducer. Optical spectrum analyzers also exist, which use direct optical techniques such as a monochromator to make measurements.

Spectrum analyzer types are dictated by the methods used to obtain the spectrum of a signal. There are swept-tuned and FFT based spectrum analyzers:

A swept-tuned spectrum analyzer uses a superheterodyne receiver to down-convert a portion of the input signal spectrum (using avoltage-controlled oscillator and a mixer) to the center frequency of a band-pass filter. With a superheterodyne architecture, thevoltage-controlled oscillator is swept through a range of frequencies, enabling the consideration of the full frequency range of the instrument.
A FFT spectrum analyzer computes the discrete Fourier transform (DFT), a mathematical process that transforms a waveform into the components of its frequency spectrum, of the input signal.

Some spectrum analyzers, such as real-time spectrum analyzers, use a hybrid technique where the incoming signal is first down-converted to a lower frequency using superheterodyne techniques and then analyzed using fast fourier transformation (FFT) techniques.

Oscilloscopes For Sale

Mixed Domain Oscilloscope - Tektronix Oscilloscopes

Oscilloscopes are used to observe the change of an electrical signal over time, such that voltage and time describe a shape which is continuously graphed against a calibrated scale. This shape is commonly referred to as a waveform, and makes it easy to view voltage changes over time, allows measurement of peak-to-peak voltage, the frequency of periodic signals, the time between pulses, the time taken for a signal to rise to full amplitude (rise time), and relative timing of several related signals.

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Because signals are often periodic and repeat (e.g. a sine wave), multiple samples which actually vary over time may appear as a seemingly continuous image (e.g. a lissajous pattern). Many oscilloscopes (storage oscilloscopes) can also capture and freeze non-repeating waveforms for a specified time interval.

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Analog Oscilloscopes

Digital Oscilloscopes

Analog Digital Oscilloscopes

Mixed Signal Oscilloscopes

Premium Test Equipment is an authorized distributor of new and used oscilloscopes from Tektronix, Agilent, B&K Precision, Fluke, Rohde & Schwarz, Extech, and many more companies. Used or leased Oscilloscopes from Agilent and Tek. We are also an authorized as a top rental company for Agilent and Tektronix, and stock a wide variety of oscilloscopes for rental for all of your needs.

Most modern oscilloscopes are lightweight, portable instruments that are compact enough to be easily carried by a single person. In addition to the portable units, the market offers a number of miniature battery-powered instruments for field service applications. Laboratory grade oscilloscopes, especially older units which use vacuum tubes, are generally bench-top devices or may be mounted into dedicated carts. Special-purpose oscilloscopes may be rack-mounted or permanently mounted into a custom instrument housing.

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Wednesday, April 9, 2014

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Tuesday, April 29, 2014