RF2140 Просмотр технического описания (PDF) - RF Micro Devices

Номер в каталоге

Компоненты Описание

производитель

RF2140

3V DCS POWER AMPLIFIER

RF Micro Devices 

the bias is fed to this pin through a short microstrip. A

bypass capacitor sets the inductance seen by the part,

so placement of the bypass cap can affect the fre-

quency of the gain peak. This supply should be

bypassed individually with 100pF capacitors before

being combined with VCC for the output stage to pre-

vent feedback and oscillations.

The RF OUT pin provides the output power. Bias for

the final stage is fed to this output line, and the feed

must be capable of supporting the approximately 1.5A

of current required. Care should be taken to keep the

losses low in the bias feed and output components. A

narrow microstrip line is recommended because DC

losses in a bias choke will degrade efficiency and

power.

While the part is safe under CW operation, maximum

power and reliability will be achieved under pulsed con-

ditions. The data shown in this data sheet is based on

a 12.5% duty cycle and a 600µs pulse, unless speci-

fied otherwise.

The part will operate over a 3.0V to 5.0V range. Under

nominal conditions, the power at 3.5V will be greater

than +32dBm at +85°C. As the voltage is increased,

however, the output power will increase. Thus, in a sys-

tem design, the ALC (Automatic Level Control) Loop

will back down the power to the desired level. This

must occur during operation, or the device may be

damaged from too much power dissipation. At 5.0V,

over +36dBm may be produced; however, this level of

power is not recommended, and can cause damage to

the device.

The HBT breakdown voltage is >20V, so there is no

issue with overvoltage. However, under worst-case

conditions, with the RF drive at full power during trans-

mit, and the output VSWR extremely high, a low load

impedance at the collector of the output transistors can

cause currents much higher than normal. Due to the

bipolar nature of the devices, there is no limitation on

the amount of current the device will sink, and the safe

current densities could be exceeded.

High current conditions are potentially dangerous to

any RF device. High currents lead to high channel tem-

peratures and may force early failures. The RF2140

includes temperature compensation circuits in the bias

network to stabilize the RF transistors, thus limiting the

current through the amplifier and protecting the

devices from damage. The same mechanism works to

compensate the currents due to ambient temperature

variations.

Rev A12 011031

RF2140

To avoid excessively high currents it is important to

control the VAPC when operating at supply voltages

higher than 4.0V, such that the maximum output power

is not exceeded.

2

2-135

Share Link: