LMH3401 Datasheet, PDF (17/48 Pages) Texas Instruments – LMH3401 7-GHz, Ultra-Wideband, Fixed-Gain, Fully-Differential Amplifier

www.ti.com
LMH3401
SBOS695A – AUGUST 2014 – REVISED DECEMBER 2014
8 Parameter Measurement Information
8.1 Output Reference Points
The LMH3401 has on-chip output load resistors. When matching the output to a 100-Ω load, the evaluation
module (EVM) uses external 40-Ω resistors to complete the output matching. Having on-chip output resistors
creates two potential reference points for measuring the output voltage. The amplifier output pins are one output
reference point (OUT_AMP). The other output reference point is the point at the matched 100-Ω load
(OUT_LOAD). These points are illustrated in Figure 49 to Figure 53; see the Test Schematics section.
Most measurements in the Electrical Characteristics tables and in the Typical Characteristics are measured with
reference to the OUT_AMP reference point. The conversion between reference points is a straightforward
correction of 3 dB for power and 6 dB for voltage, as shown in Equation 1. The measurements are referenced to
OUT_AMP when not specified.
VOUT_LOAD = (VOUT_AMP – 6 dB); and POUT_LOAD = (POUT_AMP – 3 dB)
(1)
8.2 ATE Testing and DC Measurements
All production testing and ensured dc parameters are measured on automated test equipment capable of dc
measurements only. Measurements such as output current sourcing and sinking are made in reference to the
device output pins. Some measurements such as voltage gain are referenced to the output of the internal
amplifier and do not include losses attributed to the on-chip output resistors. The Electrical Characteristics table
conditions specify these conditions. When the measurement is referred to the amplifier output, then the output
resistors are not included in the measurement. If the measurement is referred to the device pins, then the output
resistor loss is included in the measurement.
8.3 Frequency Response
This test is run with both single-ended inputs and differential inputs.
For tests with single-ended inputs, the standard EVM is used with no changes; see Figure 49. In order to provide
a matched input, the unused input requires a broadband 50-Ω termination to be connected. When using a four-
port network analyzer, the unused input can either be terminated with a broadband load, or can be connected to
the unused input on the four-port analyzer. The network analyzer provides proper termination. A network
analyzer is connected to the input and output of the EVM with 50-Ω coaxial cables and is set to measure the
forward transfer function (s21). The input signal frequency is swept with the signal level set for the desired output
amplitude.
The LMH3401 is fully symmetrical, either input (IN+ or IN–) can be used for single-ended inputs. The unused
input must be terminated.
For tests with differential inputs, the same setup for single-ended inputs is used except all four connectors are
connected to a network analyzer port. Measurements are made in either true differential mode on the Rohde &
Schwarz^® network analyzer or in calculated differential mode. In both cases, the differential inputs are each
driven with a 50-Ω source. External resistors are recommended if a matched condition is desired because the
LMH3401 does not provide an input match for 100-Ω differential sources. Both unterminated (Figure 50) and
terminated (Figure 51) differential input measurements are included in this data sheet. The termination is clearly
marked in the figure conditions.
8.4 S-Parameters
The standard EVM is used for all s-parameter measurements. All four ports are used or are terminated with
50 Ω, as in the Frequency Response section.
8.5 Frequency Response with Capacitive Load
The standard EVM is used and the capacitive load is soldered to the inside pads of the 40-Ω matching resistors
(on the DUT side). This this configuration, the on-chip, 10-Ω resistors isolate the capacitive load from the
amplifier output pins. The test schematic for capacitive load measurements is illustrated in Figure 52.
Copyright © 2014, Texas Instruments Incorporated
Product Folder Links: LMH3401
Submit Documentation Feedback
17