bipolar junction transistor - Delphijustin industries https://delphijustin.biz Making use out of things! Sat, 18 Nov 2023 22:08:48 +0000 en-US hourly 1 https://wordpress.org/?v=6.2.9 https://delphijustin.biz/wp-content/uploads/2025/10/cropped-dongwa-192-32x32.png bipolar junction transistor - Delphijustin industries https://delphijustin.biz 32 32 Basketball pump signal injector https://delphijustin.biz/basketball-pump-signal-injector/?utm_source=rss&utm_medium=rss&utm_campaign=basketball-pump-signal-injector https://delphijustin.biz/basketball-pump-signal-injector/#respond Sat, 18 Nov 2023 00:29:57 +0000 https://delphijustin.biz/?p=4844 This is a simple signal injector that can fit inside a mini basketball pump it requires: This signal injector can come in handy for repairing radios, amplifers and old TVs and also square wave generator in a probe. Later on I will make a version that uses C1 and C2 as 470nF and R3 and …

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]]> This is a simple signal injector that can fit inside a mini basketball pump it requires:

  • 1x dc blocking capacitor(10nF to 10uF) C3(2.2uF Axiel Film Capacitor)
  • 2x 100nF Capacitors C1 and C2
  • 2x 1k ohm resistors R1 and R2
  • 2x 4.7k ohm resistors R3 and R4
  • 2x General Purpose NPN low power transistors Q1 and Q2(I used PN2222A)
  • A 1.2 to 14v dc power source
  • A alligator ground clip
Circuit Diagram
The finished Device
PCB Made from Vinyl Floor tile
2.2uF DC Blocking capacitor

This signal injector can come in handy for repairing radios, amplifers and old TVs and also square wave generator in a probe. Later on I will make a version that uses C1 and C2 as 470nF and R3 and R4 as 1 Megaohm and C3 as 47uF(Since the frequency is ultralow).

The specs

Where R=R2 or R3, C=C1 or C2 and \(C_{3}\)=C3

Frequency: \(f=\frac{1}{1.38RC}=1.5kHz\)

Output AC Resistance: \(X_{C3}=\frac{1}{2\pi*fC_{3}}\)

PCB Files

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]]> https://delphijustin.biz/basketball-pump-signal-injector/feed/ 0 The simplest in-circuit transistor tester https://delphijustin.biz/the-simplest-in-circuit-transistor-tester/?utm_source=rss&utm_medium=rss&utm_campaign=the-simplest-in-circuit-transistor-tester https://delphijustin.biz/the-simplest-in-circuit-transistor-tester/#respond Thu, 10 Feb 2022 19:22:08 +0000 https://delphijustin.biz/?p=4062 This is the simplest in circuit transistor tester. It uses two ammeters to measure the transistor gain. It is kinda like the heathkit IT-18 one but uses 2 meters instead of one. I plan on using relays for the polarity switch instead of a 5PDT Rotary switch. It uses a LM317 regulator for providing a …

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]]> This is the simplest in circuit transistor tester. It uses two ammeters to measure the transistor gain. It is kinda like the heathkit IT-18 one but uses 2 meters instead of one. I plan on using relays for the polarity switch instead of a 5PDT Rotary switch. It uses a LM317 regulator for providing a very low voltage(around 1.25v). This will prevent turning on anything on and interfering with the gain measurements. The capacitor is to remove oscillations. I used two 8 cent 10nF capacitors in series to make 5nF. All [P] switches are all part of the polarity relays. I need a 4pdt relay and a spdt relay used to provide the 5pdt switch.

Circuit diagram

How do I measure the gain?

The gain is simply

$$hFE=\frac{I_c}{I_b}$$

Where hFE is your gain, Ic is your collector current and Ib is your base current I did the math with the transistor in the circuit diagram and got around 195.

Electronics Workbench Model of 2N4403
Power Supply

The collector meter is 50mA and base meter is 100uA

A video will soon come when the parts come in the mail

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