DRAM and SRAM memory

There are two types of RAM memory: SRAM and DRAM.

DRAM

DRAM uses capacitors to create the memory cell:

a capacitor is an electronic component that stores electrical energy in an electrical field. A device which can accumulate and release electrical charge.

In a DRAM cell, each bit of data is stored as a charge in a capacitor. The presence of charge represents a ‘1’ bit and the absence of charge represents a ‘0’ bit. Each of these cells is paired with a transistor that controls the reading and writing of data.

However capacitors lose charge over time due to leaks. As a result DRAM is memory that needs to be refreshed (recharged) frequently. For this reason and because it only uses one transistor and capacitor per bit, DRAM is the less expensive form of volatile memory.

SRAM

SRAM (Static Random Access Memory) is also volatile memory but its electronical implementation is different. Unlike DRAM it doesn’t use capacitors. Consequently the transistors do not leak or need to be refreshed, hence why SRAM is static and DRAM is dynamic.

SRAM uses flip flops to store the bits. It also uses multiple transistors per bit. This makes it faster than DRAM but more expensive. DRAM is at least ten times slower than SRAM.