Save $12 and learn more by building your own LT1073
Section 12L.2 invites readers of Learning the Art of Electronics to build both a boost (output voltage higher than input) and buck (output voltage is lower) switching voltage regulator using an LT1073 micropower DC-DC Converter. If you ever need a buck or boost converter in a project, the LT1073 and its sibling the LT1173 are wonderful devices. In the fixed-voltage version, you need only add an inductor, a diode, and a capacitor to the 8-pin DIP to get up to 40mA at 5V from a 1.25V source. In LAoE we use the adjustable version of the LT1073 which adds two resistors to allows us to set the output voltage to a value other than 5V or 12V. Unfortunately, the LT1073 is moderately expensive (USD$ 10.72 as of 5/2026). In addition, it hides the workings of a switching voltage converter. This is fine if you need one for a project but less ideal as a teaching exercise.
Luckily, by Chapter 11 LAoE readers have been introduced to almost all of the circuits in the blocks inside the LT1073. This means you can build the circuits in lab 11L.2 with parts you have already used (plus a MOSFET transistor on the analog parts list) and see how they go together to create a switching voltage regulator. Here is an annotated version of the block diagram of the LT1073 showing discrete replacements for the circuits inside the device.
Annotated LT1073 block diagram showing the discrete circuits used to replace the device’s internal blocks. We don’t include the x1000 amplifier optionally used to reduce ripple in Figure 11L.13 but you could use a LMC6482 to replace it as well.
By building the circuits of 11L.2 out of separate components, you also gain the ability to look at the inputs and outputs of each of these blocks, something not possible with the integrated device.
See Substitute for the LT1073 regulator on the analog parts list for complete directions on completing lab 11L.2 without the LT1073.