Uploaded January 2026 | Updated September 2026, 2 weeks ago
In this video I finally get around to describing a peculiar bit of solid-state circuit trickery that is nevertheless widely used in electronic test equipment such as multimeters, some oscilloscopes, etc. It uses a single resistor and a simple pair of plain Bipolar Junction Transistors (BJT's) to 'clamp' the post-attenuation voltage to a level that will not damage the more sensitive measuring circuitry/components. This circuit is most useful for transient overvoltage situations, but can still 'save the day' when accidental measurement situations and operator error would otherwise destroy a piece of text equipment.
I present this video NOW because I just finished posting my Heathkit IM-5225 video and one again forgot to include this bit of knowledge.
In this video I finally get around to describing a peculiar bit of solid-state circuit trickery that is nevertheless widely used in electronic test equipment such as multimeters, some oscilloscopes, etc. It uses a single resistor and a simple pair of plain Bipolar Junction Transistors (BJT's) to 'clamp' the post-attenuation voltage to a level that will not damage the more sensitive measuring circuitry/components. This circuit is most useful for transient overvoltage situations, but can still 'save the day' when accidental measurement situations and operator error would otherwise destroy a piece of text equipment.
I present this video NOW because I just finished posting my Heathkit IM-5225 video and one again forgot to include this bit of knowledge.
