Technical issues related to RF transistor SD2933:We want to use this transistor to drive piezoelectr

[H_YM]

I have the following questions and need help:

1. Can this transistor be used at a frequency of 900kHz? Can it only be used in frequency bands above 1MHz?

2. The data sheet provides a test circuit under 30MHz conditions. We do not fully understand the functions and principles of the FB2 and T2 components. Can you explain it to us? We guess that the function of this component should be for impedance conversion. Can the FB2 and T2 components be replaced with a simple and easy-to-understand transformer impedance conversion form (FT-43 core) like the previous stage?

3. Is the output of the 30MHz test circuit given by the data sheet sine wave? L1, L2 should play a low-pass filter, but I see its winding method did not understand, can you explain?

4. We want to imitate the 30MHz test circuit and apply it directly to the production environment. Are there any other issues worth noting during this process?

[AScha.3 · Accepted solution]

You dont need a special rf transistor for 900kHz working frequ.

A fast mosfet would be more up to date.

Just show the circuit, you want to use and what voltage+power should be generated.

[H_YM]

Thank you for your reply!
At present, I want to develop A wide band class A power amplifier, input 430KHz to 3MHz 1Vpp AC signal can output about 40W power, do you have any suggestions?

[AScha.3]

Sorry - but 1Vpp ??  really ?

+ class A ? why ? hi-end audio...? (i did build class A , AB and D amps for audio. 🙂 )

Need to tell a bit more details : output load is ..? for use to do...? signal should be...square wave, burst mode ..?

(Some years ago i had to build a inverter for 1 MHz , 1..100W output at 10 kV - no easy game, but worked.)

[H_YM]

At present, we have A set of power amplifier purchased from other manufacturers, the working frequency is 100KHz-3MHz, single power supply 48V, gain is about 47dB, input 1mW output 50W, input output impedance is 50 ohm, Class A power amplifier, which is composed of two mos circuit.
I want to develop a similar power supply on my own to reduce costs.
The power amplifier is used to drive the piezoelectric ceramic pieces, and I use the transformer for impedance transformation, and the load impedance can be regarded as 50 ohm.The AD9851 output sine wave, the AD8367 signal amplification output 200mV~1.4V as the signal source.

[AScha.3]

Ok , but still no info: for what is it ? What power is needed or what voltage output?

Whats the target (piezo) ? capacitance ? max. drive level?

And why sine wave ? 

+ signal source is  AD9851 , ok. But what has AD8367 , 500MHz amp, to do here ?

[H_YM]

Hello

I want to develop a high frequency linear power amplifier, with wide band, low distortion characteristics, it must be able to output at least 50W power.
I have observed that several power amplifiers in similar frequency bands (about 1MHz) on the market use two MOS tubes to do push-pull circuit output.
The load impedance being driven is 50ohm, the imaginary part is negligible (although the load is capacitive, I was able to impedance match 50ohm) The maximum drive level of the load is 40W.
Since the load is an ultrasonic atomizer, it must be driven by sine wave to have good results.
Because the output signal of the AD9851 is too small and the amplitude can only be controlled by hardware, I need the AD8367 to make a controllable gain amplifier circuit to control the output level of the signal.
In other words, the STM32 outputs the sinusoidal wave of controllable frequency through the AD9851, and controls the sinusoidal wave size through the AD8367.

[AScha.3]

Hi,

ok, now i know somewhat about the target . 

Just thinking ... 50 r load, 40W -> 48V ; needs about 136 Vss , so need +/- 70V supply, or 70V with H-bridge,

with about 2A max current; should be possible, to build something, just using 2 mosfets as output devices;

maybe (old) IRF630/IRF9630 or 2SK1058/J160 could be used for AB half-bridge at +/- 70V supply .

basically an audio amp:

BUT : how much skills / experience you have, building something like a 100W audio power amp ?

+

still no info : whats data of piezo ?

+

show circuit of 50 ohm "matching" circuit , transformer etc.

[H_YM]

hello
I am not particularly familiar with audio power amplifier, it is the first time to contact, so I hope the power amplifier circuit can be simple, similar to Figure 1(this is the online 3MHz-28MHz,100W power amplifier)
Data from the ultrasonic transducer are shown in Figure 2
The image of impedance transformation with transformer to achieve 50ohm is shown in Figure 3

[AScha.3]

Hi,

so without practice in building such an amp, i would recommend:

- if some money available, try with ready made amp module, i searched and found :

https://www.60dbm.com/product/50w-wide-band-1-55mhz-power-amplifier/

...for example, should match,what you want: 50 r output, 50W , 1MHz...

No need to buy this, you could find many others (but most expensive also).

- to learn and build , begin with some 10W amp or so...will be a long way and many killed transistors - but possible.

just an example : 50W possible, but some "funny" work, to make the transformers 🙂