Matching in power amplifier(PA)

Should the Q of matching network at the PA output as large as possible?
To keep the circuit stable, the Q is generally between 1 and 3. How to choose the Q?
should I choose 3? or just 2 is enough?

This depends by the matching topology.
In the L-networks the Q of the circuit is automatically defined when source and load impedances are set.
Pi or T networks allows to select a circuit Q independent of the source and load impedances as long as the Q chosen is larger than that which is available with the L network.

Hi,

It depend on your frequency magnitude response should be.

In General Q depend on RS, RL and component Q of each reactive element.

1. We can increase the RS and RL which will reduce the energy loss and will narrow the curve, this will increase the circuit Q and it will also increase the selectivity.

2. For fixed RS and RL , we can decrease the LC reactance by choosing lower value of inductance and large value of capacitance and again your circuit Q will increase.


Goodluck...

Thanks.
Does the T or pi matching network reduce the loss of the network?
Does higher Q mean less power loss?
I use T network and the energy loss is reduced when replace the ideal passive component with practical models.

Hi,

Not only T or Pi network, flexibility can be achieved by adding more element, but note that in terms of complexity, cost and manufacturability, simple network is better

It means increase of selectivity and narrow bandwidth


Goodluck...

how to choose a Q depend on your bandwidth, if too high, the PA is narrow band, if too low, the gain is lose, so y should choose it carefully

In my system, the f0 is 433MHz and the bandwidth is nearly 10MHz. I do not know whether I should choose higher Q, or say 3, is better.

Added after 5 minutes:

In PA design, the output port is usually matched to the load with small S-parameter, but many papers also said the PA should match to large signal S-parameters. Then how can we obtain the large signal s-parameters of the PA. We don't have such equipment for the test.

Hi,

It seems that your main goal is how to maximize the gain of your PA. and you're just corcerned that circuit Q is affecting your signal.
Take note on this one, You need to trade off when designing PA,

If you want to design a Maximum Gain Amps you have to widen its Bandwidth and same thing if the design required Narrow Band operation, you should only design High Gain Amps.

Check out your datasheet for more. You can also upload your PA to see what we can help.


Goodluck...