AV-1010 and AV-1015 Pulse Generator Applications

Models AV-1010-B, and AV-1015-B were designed to function as general-purpose laboratory work horses, as production line test equipment, and as state-of-the-art research lab equipment. These units provide peak output amplitudes of 50 or 100 Volts with rise times of 10 ns. A few typical applications are described below in order to demonstrate that these instruments are cost-effective, multi-purpose user-friendly units that belong in your instrument inventory. For faster rise time applications (100 ps and 1 ns) see Applications Note No. 2A. Give Avtech a call at 1-800-265-6681 or e-mail at info@avtechpulse.com if you need help with your applications.

LASER DIODE DRIVERS

General guidelines for obtaining 1 Amp, 2 Amp, 4 Amp and 8 Amp pulses are given in the AV-1010-B and AV-1015-B data sheets. For example, Model AV-1010-B will provide up to 2 Amp pulses in the pulse width ranges of 50 ns to 10 ms, and with the AVX-MRB6 accessory transformer will provide up to 8 Amps with pulses as wide as 10 us. Model AV-1015-B will provide 1 Amp pulses at pulse repetition frequencies as high as 10 MHz.

THE DELAY GENERATOR MODE

Models AV-1010-B and AV-1015-B all will operate in a delay generator mode as shown in Fig. 1. In this mode, the separation between the input TTL pulse and the output pulse is controlled by the delay controls while the output pulse amplitude and pulse width are controlled by the Amp and PW controls. The delays can be as low as 100 ns and as high as 10 ms.

Diagram illustrating the use of the Avtech AV-1010 or AV-1015 series of pulse generators as delay generators

Fig. 1

PULSE DRIVER-AMPLIFIER (PWOUT= PWIN)

The AV-1010-B and AV-1015-B can be triggered externally in the familiar mode where the output pulse width is controlled by the front-panel pulse width controls. However, these units can also operate in a mode where the output pulse width is equal to the input trigger pulse width, and only the output pulse amplitude is controlled by the front panel controls (or by an externally applied 0 to 10 VDC control voltage). In effect the units can act as pulse driver-amplifiers with peak outputs as high as 100 Volts. The TTL trigger pulse can be provided by your computer, a TTL IC, or by a low-power waveform generator.

Diagram illustrating the use of the Avtech AV-1010 or AV-1015 series of pulse generators as pulse amplifiers

Fig. 2


PULSE DRIVER-AMPLIFIER (VOUT = K VDC)

The output pulse amplitude for Models AV-1010-B and AV-1015-B can be controlled either by the front panel controls (and by the IEEE 488 GPIB interface) or by an externally applied 0 to +10V DC control voltage. This electronic control function (EA) will function either when the unit is triggered internally or externally (including the PWOUT = PWIN mode described in the preceding section). The input impedance to the EA port is greater than 10 kilohms, so the VDC control signal can be provided by your computer or by an ADC or from a power supply.

Diagram illustrating the use of the Avtech AV-1010 or AV-1015 series of pulse generators as voltage-controlled pulse amplifiers

Fig. 3


THE DOUBLE PULSE MODE

Models AV-1010-B and AV-1015-B all will operate in a double-pulse mode as shown in Fig. 4. In this mode, the separation between the two pulses is controlled by the delay controls (which control the separation between the SYNC pulse and main output pulse in the single pulse mode). This is a convenient feature for varied applications such as testing the performance of radar receivers, high-speed gating circuits, and mode locking applications.

Diagram illustrating the use of the double pulse mode of the Avtech AV-1010 or AV-1015 series of pulse generators

Fig. 3


DC OFFSET

Many applications require a fast pulse to be superimposed on a DC level as shown in Fig. 5. Avtech's Model AVX-TD bias insertion unit (see page 98) may be used to add a DC offset to the output of Models AV-1010-B and AV-1015-B. DC offsets as high as ±50 Volts may be employed with pulse widths as high as 100 us. The AV-1010-B is also available with a built-in offset function (the -OT option).

Diagram illustrating a method of adding a DC offset to the output of the Avtech AV-1010 or AV-1015 series of pulse generators

Fig. 4


TRANSISTOR SWITCHING TIME TESTS

Model AV-1010-B can provide pulsed output currents as high as 2 Amperes with output impedances as low as 2 Ohms, or output currents as high as 1 Amperes with an output impedance of 50 Ohms. With such high output capability (and 10 ns rise & fall times) this model is well suited for tests such as pulsing the collector (or drain) of medium power bipolar and mosfet transistors as shown in Fig. 6, or pulsing the base (or gate) of very high power bipolar (or mosfet) transistors as shown in Fig. 7. The low output impedance feature (as low as 2 Ohms) allows the unit to serve as a pulsed power supply for collector or drain biasing, and to provide switching times far less than 50 Ohms sources when used to pulse the base or gate of a power transistor. Avtech's line of bias insertion units (models AVX-TC and AVX-TD) may be used to add a DC offset to the pulse, if required. For testing applications requiring drive switching times of less than 1 ns, see the model AVR-D2-C, which is specifically designed to perform MIL-S-19500 tests.

Diagram illustrating transistor switching time tests performed using the Avtech AV-1010 or AV-1015 series of pulse generators Diagram illustrating transistor switching time tests performed using the Avtech AV-1010 or AV-1015 series of pulse generators
Fig. 6 Fig. 7


TRR AND TL TESTS FOR HIGH-SPEED RECTIFIER DIODES

The characteristic current waveform for a diode TRR (and TL) test is shown in Fig. 8, along with a definition of IF, IR, IRR, and TL. Fig. 9 illustrates a test circuit commonly specified for testing of medium and high current fast-recovery diodes. The specification often calls for a pulse generator source impedance of 10 Ohms. Avtech Model AV-1010-B will satisfy the requirement if operated in the 100 Volt range and approximately 8 Ohms is placed in series with the output. The pulser will provide an IR as high as 2 Amperes. Model AV-1015-B can also be used for applications requiring IR as high as 1 Amp. For diode switching tests requiring rise and fall times of less than 1 ns, see our AVR-EB series, which was specifically designed to perform many tests specified in MIL-STD-750C. For microwave diode TT and TL tests refer to Application Note 2A.

Diagram illustrating diode reverse recovery tests performed using the Avtech AV-1010 or AV-1015 series of pulse generators
Figs. 8 and 9


PULSE TRANSFORMER TESTING (ET CONSTANT AND PRIMARY INDUCTANCE)

Pulse generators such as the AV-1010-B and AV-1015-B along with an oscilloscope and current and voltage probes may be used to determine the ET constant of a pulse transformer using the arrangement shown in Fig. 10. The pulse width is increased until such time as the magnetizing current increases by 50% relative to the straight-line extension. The product of the applied pulse width (in ms) and amplitude (in Volts) gives the ET constant. This arrangement may also be used to determine the primary inductance. The pulse generator should be set in the low output impedance mode (ZOUT ≤ 2 Ohms) and the slope of linear portion of the magnetizing current time plot may then be used to compute the inductance as follows:

LP = EIN T1 / E1, approximately

Diagram illustrating pulse transformer tests performed using the Avtech AV-1010 or AV-1015 series of pulse generators

Fig. 10

PULSE-MODE TESTING OF GUNN DIODES

The AV-1010-B should be considered for Gunn diode pulsing, with pulse widths as low as 50 ns or as wide as 10 ms. These pulsers can source up to 2.0 Amps and feature a source impedance of less than 2 Ohms (when the amplitude range switch is in the 100 V range).

MISMATCHED LOADS, HIGH DUTY CYCLE OPERATION

The versatile AV-1010-B was specifically designed to drive loads in the range of 50 Ohms to open circuits. If the load impedance is less than 50 Ohms and the output current exceeds 120% of the rated maximum, the output stage is automatically turned off (to protect the unit). If the load impedance is 50 Ohms but the average output power exceeds the rated maximum (because the rated duty cycle is exceeded), the unit also shuts down. When the units are driving high impedance loads, the units may be operated at duty cycles at least as high as 80%. The source impedance may be set at 2 Ohms or 50 Ohms and this feature may be used to eliminate ringing when driving high impedance loads (without loss of peak amplitude). When 50 Ohm back matching is employed with a 50 Ohm load, the peak output voltage amplitude is reduced by one half (bottom trace Fig. 11B).

Click to enlarge: Waveform illustrating the Avtech pulse generator output, when a proper 50 Ohm termination is not present
Click to enlarge: Waveform illustrating the Avtech pulse generator output, when a proper 50 Ohm termination is present
Fig. 11A.
RS = 2 Ohm
RL = 100 kilohms
24" cable
Fig. 11B
RS = 50 Ohm
RL = 100 kilohm (top)
RL = 50 Ohm (bottom)


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