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For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824

Phone: 978-250-3343

Fax: 978-250-3373

Order On-line at www.hittite.com

Application Support: Phone: 978-250-3343 or apps@hittite.com

HMC992LP5E

v01.0811

IF AUTOMATIC GAIN CONTROLLER

(IF-AGC), 50 - 800 MHz

Figure 3b: Gain & Gain Conformance Error vs. VCTRL at 300 MHz, 2 attenuators + 2 amplifiers configuration.

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Gain

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Error

VCTRL (V)

Noise and Distortion

As with any multistage VGA consisting of voltage variable attenuators and gain blocks, the noise figure (NF) and input

referred distortion (IIP3) characteristics of the HMC992LP5E’s VGA are dependent on the gain control voltage VCTRL.

When the attenuation level of the variable attenuators is set to minimum (maximum gain state), the noise figure of the

HMC992LP5E’s VGA is minimized; however the IIP3 is degraded to minimum as well. The noise figure and IIP3 of the

HMC992LP5E’s VGA increases with the attenuation level of the variable attenuators.

For low attenuation levels, the noise contribution from the VGA is important since the input signal is weak. For high atten-

uation levels of the variable attenuators, the noise contribution from the VGA is less important and the noise requirement

of the VGA is relaxed since the input signal is high. The noise figure performance of the HMC992LP5E’s VGA at 300

MHz is shown in Figure 4. The HMC992LP5E’s VGA delivers a noise figure of 6 dB in its maximum gain state when it is

configured in 1 attenuator + 2 amplifiers mode.

For low attenuation levels of the variable attenuators, IIP3 is less important since high gain of whole VGA improves dis-

tortion performance at its output (OIP3). For high attenuation levels of the variable attenuators, IIP3 is more important

because of low gain of whole VGA. The distortion performance of the HMC992LP5E’s VGA at 300 MHz is shown in

Figure 4. The HMC992LP5E’s VGA provides an almost constant OIP3 of up to +44 dBm in any state when it is config-

ured in one attenuator and two amplifiers mode.

Figure 4: Noise Figure & Gain & OIP3 vs. VCTRL at 300 MHz, 1 attenuator.

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OIP3

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