SLOS823D December 2012 – March 2020 THS4531A
PRODUCTION DATA.
Figure 70 shows the general test circuit built on the EVM that was used for testing the THS4531A. For simplicity, power supply decoupling is not shown – see Layout for recommendations. Depending on the test conditions, component values are changed per Table 4 and Table 5, or as otherwise noted. Some of the signal generators used are AC-coupled 50-Ω sources and a 0.22-µF capacitor and 49.9-Ω resistor to ground are inserted across RIT on the un-driven or alternate input as shown to balance the circuit. A split-power supply is used to ease the interface to common lab test equipment, but if properly biased, the amplifier can be operated single-supply as described in the applications section with no impact on performance. For most of the tests, the devices are tested with single ended input and a transformer on the output to convert the differential output to single ended because common lab test equipment have single ended inputs and outputs. Performance is the same or better with differential input and differential output.
GAIN | RF | RG | RIT |
---|---|---|---|
1 V/V | 2 kΩ | 2 kΩ | 51.1 Ω |
2 V/V | 2 kΩ | 1 kΩ | 52.3 Ω |
5 V/V | 2 kΩ | 392 Ω | 53.6 Ω |
10 V/V | 2 kΩ | 187 Ω | 57.6 Ω |
RL | RO | ROT | ATTEN (dB) |
---|---|---|---|
100 Ω | 25 Ω | open | 6 |
200 Ω | 84.5 Ω | 71.5 Ω | 16.7 |
500 Ω | 237 Ω | 56.2 Ω | 25.6 |
1 kΩ | 487 Ω | 52.3 Ω | 31.8 |
2 kΩ | 976 Ω | 51.1 Ω | 38 |
Because of the voltage divider on the output formed by the load component values, the output of the amplifier is attenuated. The column ATTEN in Table 5 shows the attenuation expected from the resistor divider. When using a transformer at the output as shown in Figure 70, the signal has slightly more loss because of transformer insertion loss, and these numbers are approximate. The standard output load used for most tests is 2 kΩ with associated 38 dB of loss.