BD676, BD676A, BD678, BD678A, BD680, BD680A, BD682, BD682T Details

Plastic Medium-Power Silicon PNP Darlingtons

        This series of plastic, medium−power silicon PNP Darlington transistors can be used as output devices in complementary general−purpose amplifier applications.

Features
• High DC Current Gain − hFE = 750 (Min) @ IC = 1.5 and 2.0 Adc
• Monolithic Construction
• BD676, 676A, 678, 678A, 680, 680A, 682 are complementary with BD675, 675A, 677, 677A, 679, 679A, 681
• BD678, 678A, 680, 680A are equivalent to MJE 700, 701, 702, 703
• Pb−Free Package are Available*

Inside the 555

Note: Pin 7 is "in phase" with output Pin 3 (both are low at the same time).
Pin 7 "shorts" to 0v via a transistor. It is pulled HIGH via R1.
Maximum supply voltage 16v - 18v
Current consumption approx 10mA
Output Current sink @5v = 5 - 50mA @15v = 50mA
Output Current source @5v = 100mA @15v = 200mA
Maximum operating frequency 300kHz - 500kHz


Faults with Chip:
Consumes about 10mA when sitting in circuit
Output voltage can be up to 2.5v less than rail voltage
Output can be 0.5v to 1.5v above ground
Sources up to 200mA
Some chips sink only 50mA, some will sink 200mA

A NE555 was tested at 1kHz, 12.75v rail and 39R load.
The Results:
Output voltage 0.5v low, 11.5v high at output current of 180mA
The "test chip" performance was excellent.


HOW TO USE THE 555
        There are many ways to use the 555. They can be used in hundreds of different circuits to do all sorts of clever things. They can also be used as three different types of oscillators:
(a) Astable Multivibrator - constantly oscillates
For frequencies above 1 cycle per second, it is called an oscillator (multivibrator or square wave oscillator).
For frequencies below 1 cycle per second it is called a TIMER or DELAY.
(b) Monostable - changes state only once per trigger pulse - also called a ONE SHOT
(c) Voltage Controlled Oscillator - called a VCO.

The 555 Pins

Here is the identification for each pin:

             

    

When drawing a circuit diagram, always draw the 555 as a building block, as shown below with the pins in the following locations. This will help you instantly recognise the function of each pin:


 


Pin 1 GROUND. Connects to the 0v rail.
Pin 2 TRIGGER. Detects 1/3 of rail voltage to make output HIGH. Pin 2 has control over pin 6. If pin 2
is LOW, and pin 6 LOW, output goes and stays HIGH. If pin 6 HIGH, and pin 2 goes LOW, output goes
LOW while pin 2 LOW. This pin has a very high impedance (about 10M) and will trigger with about 1uA.
Pin 3 OUTPUT. (Pins 3 and 7 are "in phase.") Goes HIGH (about 2v less than rail) and LOW (about
0.5v less than 0v) and will deliver up to 200mA.
Pin 4 RESET. Internally connected HIGH via 100k. Must be taken below 0.8v to reset the chip.
Pin 5 CONTROL. A voltage applied to this pin will vary the timing of the RC network (quite
considerably).
Pin 6 THRESHOLD. Detects 2/3 of rail voltage to make output LOW only if pin 2 is HIGH. This pin
has a very high impedance (about 10M) and will trigger with about 0.2uA.
Pin 7 DISCHARGE. Goes LOW when pin 6 detects 2/3 rail voltage but pin 2 must be HIGH. If pin 2 is
HIGH, pin 6 can be HIGH or LOW and pin 7 remains LOW. Goes OPEN (HIGH) and stays HIGH when
pin 2 detects 1/3 rail voltage (even as a LOW pulse) when pin 6 is LOW. (Pins 7 and 3 are "in phase.")
Pin 7 is equal to pin 3 but pin 7 does not go high - it goes OPEN. But it goes LOW and will sink about
200mA. You can connect pin 7 to pin 3 to get a slightly better SINK capability from the chip.
Pin 8 SUPPLY. Connects to the positive rail.





555 in a circuit - note the circle on the chip to identify pin 1. This is sometimes called a "push-out-pin" (hole) and sometimes it has no importance. But in this case it represents pin 1.