RFQ/BOM 0 로그인 / 등록하다

귀하의 위치를 선택하세요

사용자 이미지

The self-locking circuit formed by the triode automatically works without the on signal.

Hardware design
9월 17, 2020 by Trish 853

As shown in the figure, the self-locking circuit. When simulating on Multisim, it is found that if the resistance R2 is selected too large (for example, more than 10K), the LED will be on when the simulation starts; if R2 is selected appropriately (for example, below 1K), it will work normally , The light is off when the power is on, the light is on when the switch is pressed, and the light remains on when the button is released. Now I want to know how this R2 affects the circuit.

모든 댓글

user image

Sinclair 게시 날짜 September 17, 2020

The power-on conduction is the result of positive feedback by the leakage current of the two transistors. The function of R2 is to connect the leakage current of Q2 to the ground, so that the base of Q1 is lower than the turn-on voltage and cannot be turned on, but only leakage current.

The size of R2 can be appropriately selected according to the size of the leakage current. If the leakage current is large, the resistance must be small, so that Q1 cannot be turned on, thereby preventing the effect of positive feedback.

0
user image

Chauncy 게시 날짜 September 17, 2020

I have seen this circuit before. The reason why the value of R2 is too large, which causes the LED to turn on when powered on, is because there is a leakage current in Q2, which generates a relatively large voltage drop on R2, thus turning on Q1.

0
user image

Agnieszka 게시 날짜 September 17, 2020

Determined by the characteristics of the triode element.

0

답변 작성

답글을 달려면 로그인이 필요합니다. 로그인 | 등록하다