Sequential LED circuit using LM358 and MOSFETs/BJTs without 555 timer or decoder

The discussion addresses building a sequential LED lighting circuit using an LM358 operational amplifier and MOSFETs or BJTs without employing a 555 timer or decoder ICs. The original request involves lighting a series of six LEDs sequentially with a one-second delay between each, culminating in all LEDs being lit simultaneously and then blinking in unison continuously. Suggestions highlight the complexity of achieving this solely with linear components like op-amps and transistors, noting that typical solutions use digital ICs such as 555 timers, decade counters (e.g., CD4017), or microcontrollers. However, given the constraint to use only op-amps, MOSFETs, and BJTs, the conversation explores alternative approaches including constructing flip-flops and ring counters from discrete transistors and op-amps, forming oscillators with BJTs, and implementing feedback loops to create sequential logic. One approach involves designing a ring oscillator to drive transistor-based flip-flops for sequential LED activation, with a bistable multivibrator to switch modes for simultaneous blinking. References to using light-dependent resistors (LDRs) in ring counters and recreating 555 timer functionality with op-amps and transistors are also mentioned. The discussion includes conceptual circuit hints and encourages iterative building starting with fewer LEDs to scale up. Overall, the thread emphasizes the challenge and creativity required to implement sequential LED control using only analog components and discrete transistors without standard digital ICs.
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