Calculate Voltage

2011-09-11 1:39 pm

a 5V square wave digital source has 1k Ohm source resistance and is measured with a 50 Ohm input impedance oscilloscope. What is the signal swing measured?

Here is the circuit my teacher gave me.

圖片參考：http://imgcld.yimg.com/8/n/HA00799676/o/701109110014513873456370.jpg
And here is the solution my teacher gave the class:

Vm = R_L/(R_i + R_L) = 50/(1000+50)
Vm = 3V

But I totally don't understand. If anyone can solve it in other way or help me to understand, I will be so glad. Really hope to learn the concept and how he did it.

回答 (1)

用戶9437

2011-09-14 12:56 am

✔ 最佳答案

我已經有8 年無看過電子的書了, 試一試答吧.

這條提目之中:

1. 電流是恆定的 (假如有電流的話), 而且是簡單的串聯電路.

2. 因為只有一個emf source, 所以, 5V的emf會被2個電阻分配了.

3. 因此, 我們可以引用 V=Ir 的公式,

Vtotal / Rtotal = Vemf / Remf = Vocr / Rocr
5 / ( 1000 + 50 ) = Vemf / 1000 = Vocr / 50
Vemf = 4.761
OCR應該度到 4.761V
而OCR自已食左0.291V

我不知道你抄的提示有沒有抄錯, 不過, 3V / 5V是60%, 2個內阻的差距比例是 1000 / 50 = 2000%, 你認為「大2000%只能分到60%」這樣的比例合理嗎?

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