1-to-3 transistor circuit design projects

[rommelpm]

Kindly post all circuits that you have successfully designed/assembled and tested either by simulation or by actual prototype using up to three transistor devices.

The application could range from a simple audio amplifier, pre-amps, active-filters, basic power supplies, switch mode power supplies, transmitters, robotics...etc   

[rommelpm]

My experimental active BJT lowpass filter for my Subwoofer:



I actually extracted the basic circuit from the internal circuitry of an IC from which I added Q1 as voltage amp and Q3 as buffer circuit.  For the past 3 years, this circuit is still up and running. 

[rommelpm]

SCR equivalent in the BJT world.



During those times when I need the functionality of an SCR, I just go and salvage some old transistor circuits! 

['yus]

ang walang kamatayang Astable Multivibrator circuit:


pwedeng gamitin as (push-pull) oscillator o kaya simpleng LED flasher:

[Shey]

first multivibrator LED Flasher ko na ginawa ay nung 1992 pa hehehehe

['yus]

pwede rin ang one-bjt negative resistance oscillator:

http://www.electronicslab.ph/forum/index.php?topic=2199.0

[rommelpm]

This is my experimental Differential Amp Preamplifier that I used as input for my guitar amp:



Kadalasang BJT preamps na nakikita ko ay either a single stage CE amp or multistage CE and CC combinations. So I just tried this for a change.

Note: the Hfe for all transistors used in this circuit where assumed to be 100.

['yus]

pwede rin ang simple analog Mosfet ORing control:
(simple invention by: Bruce Frederick and Daryl Weispfennig)


pwede nyo itong gawing kung gusto nyong mag-parallel ng dalawang high-current power supply.
yung Q3 will act as "ideal" ORing diode, kaya dapat high current ang rating nya,
saka very low din ang kanyang drain-to-source ON resistance..
yung Q1 & Q2 naman pwedeng general purpose NPN lang, pero dapat ma-match yung temperature nila,
and as suggested, kung pwede dapat iisang package lang sila (like 6-pin sot-23 for thermal tracking).
for detailed explaination ng circuit operation, search nyo na lang sa net (e.g. freepatentsonline).

[rommelpm]

12 VOLTS FLOURESCENT INVERTER  Posted by Electron from: (www.electronicslab.ph/forum/index.php?topic=87.0)
http://www.talkingelectronics.com/projects/FluorescentInverter/FluorescentInverter.html

Other interesting circuits:

12 Volts Solar Charger circuit
http://www.talkingelectronics.com/projects/SolarCharger/SolarCharger.html

Solar Garden Light
http://www.talkingelectronics.com/projects/SolarLight/SolarLight.html

5V Solar power supply-I
http://www.talkingelectronics.com/projects/PowerSupply5vSolar/PowerSupply5vSolar.html

5V Solar power supply-II
http://www.talkingelectronics.com/projects/PowerSupply5vSolar/PowerSupply5vSolar-2.html

[rommelpm]

A Simple transistorize Sinewave Oscillator:



Upon powering up the circuit, the LC tank will oscillate at its natural resonance until it will decay unless it will be reinforced.

F = 1/(2 x pi x [LC]^1/2 )
F = 1.59 Khz

To enable the circuit to continuously oscillate, it needs to be reinforced by returning back the signal to the amplifier. And this can be done through R2 (or even the internal resistance = re).

The oscillation voltage from the tank circuit is being reflected across R2 while R2  serves as an input to the BJT circuit, thus oscillation process will start.

transistor Hfe=100 or higher
R1 can be from 1k to 10K
R2 can be any value lower from 1 to 10ohms. You can also remove this, utilizing only the internal re

From the simulation results:
    F = 1.6 Khz,  3.8Vpp

 

[mArKhAo]

w0w. 

[rommelpm]

My Led-Bulb version



I bought a cheap portable rechargeable flashlight and somehow the filament lamp was easily busted.

With some spare White-LEDS that I got a few years back from one of the suppliers (that was 2 dollars each in 1997) I came up with this circuit.

The circuit uses a constant current source to protect the white LEDs from being over driven. Though I should have used a simple Resistor just to limit the current, I am not quit convinced that the internal circuitry of the flashlight would reliably produce a fix voltage especially when recharging it with a 220V source.
 

[1110000]

pede rin boost yan lalagyan ng coil

[1110000]

[Macgyver]

My Led-Bulb version



I bought a cheap portable rechargeable flashlight and somehow the filament lamp was easily busted.

With some spare White-LEDS that I got a few years back from one of the suppliers (that was 2 dollars each in 1997) I came up with this circuit.

The circuit uses a constant current source to protect the white LEDs from being over driven. Though I should have used a simple Resistor just to limit the current, I am not quit convinced that the internal circuitry of the flashlight would reliably produce a fix voltage especially when recharging it with a 220V source.
 

Paano naderive yung 38mA?

[rommelpm]

Paano naderive yung 38mA?

The voltage drop at R1 is VR1= vd1+vd2 - vbe

vd1 = vd2 = voltage drop across the 1n4148
vbe = transistor base to emitter voltage

VR1 = 0.7 + 0.7 - 0.7 = 0.7

IR1 = VR1/R1 = 0.7/18
IR1 = 0.038A 
IR1 = 38mA 

 

[rommelpm]

pede rin boost yan lalagyan ng coil

Hmm! interesting ckt, pero ano yung tested  value/ratio nang transformer? ferrite core ba to? at what frequency is this operating? It looks similar to a boost-converter without the capacitor. 

[ahlburuto]

My Led-Bulb version



I bought a cheap portable rechargeable flashlight and somehow the filament lamp was easily busted.

With some spare White-LEDS that I got a few years back from one of the suppliers (that was 2 dollars each in 1997) I came up with this circuit.

The circuit uses a constant current source to protect the white LEDs from being over driven. Though I should have used a simple Resistor just to limit the current, I am not quit convinced that the internal circuitry of the flashlight would reliably produce a fix voltage especially when recharging it with a 220V source.
 

bakit di pwedeng resistor na lang ilagay? tanong lang...

[rommelpm]

bakit di pwedeng resistor na lang ilagay? tanong lang...

Pwede  naman basta siguradong fix ang voltage source. heto kasing rechargeable flashlight na pinaggamitan ko ay mukhang unstable lalo't directa sa 220V ang pag recharge nito. 

[ahlburuto]

ah ok.... kaya pala me ganun pa.... yun kasing mga ginagawa ko eh resistor lang. ginadahan ko lang ang housing kasi nilagay ko sa kisame ng bahay ko.

br