Can R4 be replaced with a jumper in an ultrasonic generator circuit?

[javi2018]

I let you a circuit that is an ultrasonic generator to 500 khz, you feel free to include some improvement.

 

[berkeman]

I let you a circuit that is an ultrasonic generator to 500 khz, you feel free to include some improvement.
View attachment 214672

Welcome to the PF.

Where did you get the schematic? Can you describe how it works in detail? Can you provide a datasheet for the ultrasonic transducer? Have you simulated this circuit using a SPICE package? Did you run a Monte Carlo simulation as part of the SPICE simulations?

 

[javi2018]

I found the schematic navigating the internet and with trial error I was manipulating the values until I adjusted them, I tested the circuit in OrCad (pspice) but without buzzer, the piezoelectric disk that I used is 1.7Mhz and a static capacitance of 1800pF but I do not have a datasheet for this, which it are used for water atomization.
I'm not an engineer, so I can not clarify much more how it works, I just wanted to share it with others.

 

[tech99]

I let you a circuit that is an ultrasonic generator to 500 khz, you feel free to include some improvement.
View attachment 214672

R1 seems to be in the wrong position to provide DC stabilisation of the transistor. R4 does not seem necessary.
Not sure why the circuit is so complicated. I am not certain of the basic concept of this oscillator as it has components sprinkled everywhere.

 

[Borek]

R4 does not seem necessary.

Unless I am missing something R2, R3 and R4 can be replaced by a single 18k resistor.

 

[Tom.G]

R1 seems to be in the wrong position to provide DC stabilisation of the transistor.

It's not meant to, it is for current sensing.

Overall, the circuit seems a modification of the Butler Emitter Follower oscillator. I seem to recall similar circuits in ultrasonic cleaners but I don't remember the specifics; it was many years ago.

 

[javi2018]

Indeed, I forgot to comment, the circuit I extracted from a web of ultrasonic cleaners.

 

[CWatters]

Unless I am missing something R2, R3 and R4 can be replaced by a single 18k resistor.

Yes somethings up with that bit.

R4 (100R) is less than 1% of R2//R3. Can't see why the overall resistance is that critical.

 

[Borek]

Yes somethings up with that bit.

R4 (100R) is less than 1% of R2//R3. Can't see why the overall resistance is that critical.

Even assuming R2 and R3 to be 1% resistors, variability of their equivalent resistance is larger than 100 Ω (trivial estimate suggests it should be somewhere in the 17.7-18.1 kΩ).

 

[jim hardy]

Even assuming R2 and R3 to be 1% resistors, variability of their equivalent resistance is larger than 100 Ω (trivial estimate suggests it should be somewhere in the 17.7-18.1 kΩ).

and 18K is a standard value.

I'd guess R4 is just a jumper to get signal across a PCB track.