Why does an increasing demand for dollars lead to the depreciation of a currency? I am self studying some slides of a course on monetary economics.

The source of the slides is Pilbeam, chapter 11 on the mechanism of the Bretton Woods system.

I don't understand the following reasoning:

Suppose there is an increasing demand for dollars in some country (because of a shortage on the current account).
This will lead to the depreciation of the currency.
I am by no means an expert in monetary policy, but this is how I understand it. An increasing demand for dollars implies that more people want to trade the local currency for dollars. The supply of the local currency then increases while demand for it decreases, implying that the currency will depreciate.