A fluid supply device for providing a mobile phase for a sample separating device includes, a supply conduit for providing a fluid which forms at least a part of the mobile phase, a fluid valve which is fluidically coupled with the supply conduit and, depending on its switching state, enables or prevents a passing of the fluid from the supply conduit, an elastic buffer unit which is fluidically coupled upstream of the fluid valve with the supply conduit and which is configured for buffering the fluid, and a fluid conveying unit for conveying the fluid which passes the fluid valve.