| Electronics > Projects, Designs, and Technical Stuff |
| Active voltage divider? |
| << < (3/3) |
| David Hess:
You already have transistors buffering 2 of the 3 reference nodes but the tail current of those differential pairs will have to be lowered also. The reference nodes could be buffered with micropower low input bias current operational amplifiers configured as voltage followers. That would get into the 10s of microamps range of supply current. Two of them replace Q1, R10, Q2, and R11 to drive the emitters of Q3 and Q4 directly. Problem solved. |
| spec:
--- Quote from: hlavac on December 18, 2018, 05:34:17 pm ---I was thinking more like two LR44 cells to make it small :) Switching supply would consume power and would need to be turned on/off --- End quote --- --- Quote from: hlavac on December 18, 2018, 05:40:55 pm ---I mean, I don't need it to run on 5V. Was looking into reference chips like LT1004 to provide reference 2.5V, so I can run on 3V from two LR44... It should only consume significant power when a LED is lit :) --- End quote --- Understand. My approach would use two high speed comparators with CMOS inputs and would consume around 5mA including LEDS. I was thinking of a CR3 LiIon rechargeable cell for the PSU. But this approach is not in line with your thinking. Getting back to your original question of the low power reference voltage. The solution is quite simple. All you need is a dual, micro power opamp with hi Z inputs configured as unity gain buffers. Then you can increase the divider chain resistance and use the buffers to provide a low z source for the bases of the transistor comparators in your original design. These opamps may be of interest, but there are lower power types: TLV2241, 42, 44 LM0462, 64 TSV711, 12, 14 TSU111, 12 MCP606, 08, 07, 09 MAX9910, 11, 12 : |
| Navigation |
| Message Index |
| Previous page |