THS4521 datasheet(26/71 Pages) TI2

26 / 71 page

THS452x

49.9 W

1kW

49.9 W

OCM

IN+

Installedto

Balance

Amplifier

Open

From

50-

Source

OUT-

OUT+

ToOscilloscope

with50-

Input

S+

S-

0.22 F

THS452x

OCM

OUT

Installedto

Balance

Amplifier

Open

1:1

From

50-

Source

IN+

0.22 F

To50-

Test

Equipment

S-

S+

49.9 W

THS4521, THS4522, THS4524

SBOS458H – DECEMBER 2008 – REVISED JUNE 2015

www.ti.com

Feature Description (continued)

8.3.2 Distortion

The circuit shown in Figure 55 is used to measure harmonic and intermodulation distortion of the amplifier.

A signal generator is used as the signal source and the output is measured with a Rhode and Schwarz spectrum

analyzer. The output impedance of the HP signal generator is ac-coupled and is 50

Ω. RIT and RG are chosen to

impedance match to 50

Ω and maintain the proper gain. To balance the amplifier, a 0.22-μF capacitor and 49.9-

Ω resistor to ground are inserted across RIT on the alternate input.

A low-pass filter is inserted in series with the input to reduce harmonics generated at the signal source. The level

of the fundamental is measured and then a notch filter is inserted at the output to reduce the fundamental so it

does not generate distortion in the input of the spectrum analyzer.

The transformer used in the output to convert the signal from differential to single-ended is an ADT1–1WT. It

limits the frequency response of the circuit so that measurements cannot be made below approximately 1 MHz.

Figure 55. Distortion Test Circuit

8.3.3 Slew Rate, Transient Response, Settling Time, Output Impedance, Overdrive, Output Voltage, and

Turn-On/Turn-Off Time

The circuit shown in Figure 56 is used to measure slew rate, transient response, settling time, output impedance,

overdrive recovery, output voltage swing, and ampliifer turn-on/turn-off time. Turn-on and turn-off time are

measured with the same circuit modified for 50-

Ω input impedance on the PD input by replacing the 0.22-μF

capacitor with a 49.9-

Ω resistor. For output impedance, the signal is injected at VOUT with VIN open; the drop

across the 2x 49.9-

Ω resistors is then used to calculate the impedance seen looking into the amplifier output.

Figure 56. Slew Rate, Transient Response, Settling Time, Output Impedance, Overdrive Recovery, VOUT

Swing, and Turn-On/Turn-Off Test Circuit

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Product Folder Links: THS4521 THS4522 THS4524

THS4521 Datasheet(PDF) 26 Page - Texas Instruments

THS4521 Datasheet(HTML) 26 Page - Texas Instruments

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