Monday, August 30, 2021

LDO low voltage - pinned vs surface mount components

I was planning a single cell radio. The previous oscillator was looking good but will need a little more thought. In the mean time I am looking at the LDO for the single cell radio. My parts bin is fairly well stocked but I am having to decide between surface mount, pinned component or using 3 volts? (the original plan was 1 cell) This series of post show the options.

3 volts both pinned
2 volts both pinned.
1.5 volts 1 surface and 1 pinned.
2 volts both surface mount.
2 volt 1 pinned 1surface mount.
1.5 volts 1 surface 1 pinned.

So I can obtain the goal of a 1.5 volt LDO by using 1 surface mount and 1 pinned Jfet or I can move the goal and use 2 cells.


  1. My designs now are geared towards using Li-Ion, 3.7-4.2 volts. They are easy to recharge and are becoming more affordable. Discarded cell phone charger are also plentiful.

  2. I bought a 6 volt lantern battery which had been dropped (or otherwise mistreated). It was 4.5 volts. I opened it up and found a shorted cell. The positive terminal bonding strap was pressed against the shell. I had 3 cells looking for a project. My first project was to use 1 cell. I put the K2539 and J175 Lamda on a board and connected it to my bench power supply. The thing sings at a little over 1.5 volts so I am modifying the project to use 3 volts.

  3. So I have a 3 volt supply and Lambda Diode to feed a DBM.
    The common problem with a direct conversion radio made with the DBM is the Local Oscillator and the RF signal are the same frequency so the oscillator must be shielded to prevent overloading the RF circuit.
    One simple work around is to use an IF to off set the signals.
    So the project shifts course.