LM293输出不是高低电平
如图所示,我把LM393替换成LM293,我的认知是当+端电压大于﹣端电压,输出高电平,当+端电压小于﹣端电压时,输出低电平,但是在实际应用中,电压输出不是跳变的,在+端电压开始接近﹣端电压还有0.6伏左右的时候,输出端就开始有电压输出,并且从0开始慢慢增大,一直到所谓的高电平
不知道是我对比较器的认知是错误的,还是电路设计有问题。困扰了我很久了,求解惑啊
首先先确定输入是否都在共模电压范围之内,不同的两输入,输出情况在datasheet中都有给出,
1. When both IN- and IN+ are both within the common-mode range:
(a) If IN- is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking current
(b) If IN- is lower than IN+ and the offset voltage, the output is high impedance and the output transistor is not conducting
2. When IN- is higher than common-mode and IN+ is within common-mode, the output is low and the output transistor is sinking current
3. When IN+ is higher than common-mode and IN- is within common-mode, the output is high impedance and the output transistor is not conducting
4. When IN- and IN+ are both higher than common-mode, the output is low and the output transistor is sinking current。
感谢你的回答,LM293的共模电压问题我也看过,应该不是这个问题。现在是+输入端小于﹣输入端,比如,+输入端电压4.13V,﹣输入端电压4.35V,结果输出端电压时3.05V(工作电压时8.5V)这个电压会随+端输入电压增大而增大,减小而减小,而不是那种脉冲般的跳变。这才是我纠结的地方。另外,两个输出端,一个驱动三极管,一个驱动门电路。
LM293是OC输出,输出端有没有加上拉电阻?我怀疑您的输出端没有上拉,我用TINA仿真了一下,没问题。