1 Watt HF Class A Buffer Amp - Part 1

 I'm slowly assembling pieces for an 80m Weaver based transceiver.  It's really hot now in the workshop with summer arriving so I retreat to the house after 9am. The receiver is taking shape so I'm turning my attention to the transmitter while in the house.

Reviewing the 1 Watt Class A buffer I have used in previous projects I found obsolescence had arrived. While I still had some of these transistors in the parts bin it felt appropriate to cast around to see what else was out there.

1Watt HF Buffer - Class A

While this amplifier has served me well I'm going to let myself be distracted and test how this amplifier chain works with transistors readily available today.

Q4 could be a SOT23 device. I've got plenty I can try and it's not worth agonising over. Q5 should be something more substantial to cope with the heat it will dissipate. Easily found I've ordered a couple of types of SOT89 transistors for Q5.

Q6 dissipates around 1.5W so I wanted something capable of handling at least 2W. I think I have found suitable transistors though the package of each is different.

Let the testing begin! 

73's

Richard

Noise in "Jelly Bean" regulators - conclusion

Some rules of thumb emerged from my investigations:

1. If the data sheet makes no mention of a regulators output voltage noise then it's going to be horrible until confirmed otherwise. Maybe only good for digital projects.
   
   
2. Any 78Lxx or LM317 type regulator followed by a  capacitance multiplier will deliver a clean supply voltage for low power analogue circuits. But the voltage drop of the capacitance multiplier needs to be either adjusted out or allowed for.
   
   
3. A TL431 is a worthy alternative, and with a capacitance multiplier will deliver a cleaner supply voltage for demanding applications. 

My new standard for low noise regulation is the TL431 and capacitance multiplier. 

73's

Richard